Display device

ABSTRACT

A display device may include a light emitting element, a buffer layer, a gate insulation layer, and a switching element. A refractive index of the gate insulation layer may be equal to a refractive index of the buffer layer. The switching element may be electrically connected to the light emitting element and may include an active layer and a gate electrode. The active layer may be positioned between the buffer layer and the gate insulation layer and may directly contact at least one of the buffer layer and the gate insulation layer. The gate insulation layer may be positioned between the active layer and the gate electrode and may directly contact at least one of the active layer and the gate electrode.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 USC §119 to Korean PatentApplication No. 10-2016-0011355, filed on Jan. 29, 2016 in the KoreanIntellectual Property Office (KIPO); the contents of the Korean PatentApplication are incorporated herein in by reference.

BACKGROUND

1. Field

The technical field is related to a display device, e.g., an organiclight emitting display device.

2. Description of the Related Art

Various display devices have been widely used in electronic devices.Display devices may include liquid crystal display (LCD) devices andorganic light emitting display (OLED) devices.

A display device, such as an OLED device, may include a substantiallytransparent region for showing an object (or a target) that is locatedin the rear (e.g., the back) of the display device. The display devicemay also include a pixel region that can emit light for displaying animage. Multiple insulation layers may be disposed in both thetransparent region and the pixel region. Refractive indexes of theinsulation layers may be substantially different from each other.Therefore, transmissivity of the transparent region may beunsatisfactory. In addition, color characteristics associated with alight transmitted via the transparent region may be undesirably changed.One or more of the insulation layers may be based on nitride, maydirectly contact an active layer of the display device, and maynegatively affect electron mobility of the active layer, such thatperformance of the display device may be unsatisfactory.

SUMMARY

Embodiments may be related to a display device, e.g., an organic lightemitting display device, with satisfactory transmittance in asubstantially transparent region of the display device.

Embodiments may be related to a display device, e.g., an organic lightemitting display device, with satisfactory electron mobility in aswitching element of the display device.

According example embodiments, a display device, e.g., an organic lightemitting display (OLED) device, includes a substrate, a buffer layer, afirst gate insulation layer, an active layer, a first gate electrode, afirst insulating interlayer, source and drain electrodes, and a pixelstructure. The substrate includes a sub-pixel region (which correspondsto a sub-pixel of the display device) and a transparent region (which issubstantially transparent). The buffer layer is disposed in thesub-pixel region and the transparent region on the substrate, and has afirst refractive index. The first gate insulation layer is disposed inthe sub-pixel region and the transparent region on the buffer layer, andincludes the same material(s) as the buffer layer. The active layer isdisposed between the buffer layer and the first gate insulation layer.The first gate electrode is disposed on the first gate insulation layerunder which the active layer is disposed. The first insulatinginterlayer covers the gate electrode on the first gate insulation layer,and is disposed in the sub-pixel region and the transparent region. Thefirst insulating interlayer has a second refractive index that isgreater than the first refractive index. The source and drain electrodesare disposed on the first insulating interlayer, and define a switchingelement together with the active layer and the first gate electrode. Thepixel structure is disposed on the switching element, and iselectrically connected to the switching element.

In example embodiments, the first refractive index may be in a rangefrom 1.4 to 1.5, and the second refractive index may be in a range from1.7 to 1.8.

In example embodiments, an upper surface of the active layer may be incontact with the first gate insulation layer, and a lower surface of theactive layer may be in contact with the buffer layer.

In example embodiments, the substrate may include transparent insulationmaterial(s).

In example embodiments, the substrate may consist essentially of atransparent polyimide substrate that has a refractive index in a rangefrom 1.7 to 1.8.

In example embodiments, the substrate may include a transparentpolyimide layer and a barrier layer, and the barrier layer may beinterposed between the transparent polyimide layer and the buffer layer.The barrier layer and the first insulating interlayer may include thesame material(s).

In example embodiments, the barrier layer may include organicmaterial(s) or inorganic material(s) that have a refractive index in arange from 1.7 to 1.8.

In example embodiments, the barrier layer may consist essentially ofsilicon oxynitride that has a refractive index in a range from 1.7 to1.8.

In example embodiments, the silicon oxynitride may consist essentiallyof silicon, oxygen, and nitrogen in a weight ratio of about 3.95:1:1.7.

In example embodiments, each of the buffer layer and the first gateinsulation layer may include organic material(s) or inorganicmaterial(s) that have a refractive index in a range from 1.4 to 1.5.

In example embodiments, each of the buffer layer and the first gateinsulation layer may consist essentially of silicon oxide that has arefractive index in a range from 1.4 to 1.5.

In example embodiments, the active layer may consist essentially ofamorphous silicon or polysilicon.

In example embodiments, the first insulating interlayer may includeorganic material(s) or inorganic material(s) that have a refractiveindex in a range from 1.7 to 1.8.

In example embodiments, the first insulating interlayer may consistessentially of silicon oxynitride that has a refractive index in a rangefrom 1.7 to 1.8.

In example embodiments, the silicon oxynitride may consist essentiallyof silicon, oxygen, and nitrogen in a weight ratio of about 3.95:1:1.7.

In example embodiments, the OLED device may further include a secondgate insulation layer. The second gate insulation layer may beinterposed between the first gate insulation layer and the firstinsulating interlayer, and may be in the sub-pixel region and thetransparent region.

In example embodiments, the second gate insulation layer and the firstinsulating interlayer may include the same material(s).

In example embodiments, the second gate insulation layer may consistessentially of silicon oxynitride that has a refractive index in a rangefrom 1.7 to 1.8.

In example embodiments, the silicon oxynitride may consist essentiallyof silicon, oxygen, and nitrogen in a weight ratio of about 3.95:1:1.7.

In example embodiments, the OLED device may further include a secondgate electrode. The second gate electrode may be interposed between thesecond gate insulation layer and the first insulating interlayer, andmay be disposed on the second gate insulation layer under which thefirst gate electrode.

In example embodiments, the OLED device may further include a secondinsulating interlayer. The second insulating interlayer may beinterposed between the first insulating interlayer and the source anddrain electrodes, and may be in the sub-pixel region and the transparentregion. The second insulating interlayer may have the first refractiveindex.

In example embodiments, the second insulating interlayer may consistessentially of silicon oxide that has a refractive index in a range from1.4 to 1.5.

In example embodiments, the OLED device may further include a secondgate electrode. The second gate electrode may be interposed between thefirst insulating interlayer and the second insulating interlayer, andmay be disposed on the first insulating interlayer under which the firstgate electrode is disposed.

In example embodiments, the OLED device may further include aplanarization layer. The planarization layer may cover the source anddrain electrodes on the first insulating interlayer.

In example embodiments, the planarization layer may be disposed in thesub-pixel region on the first insulating interlayer, and may expose thetransparent region.

In example embodiments, the planarization layer may be disposed in thesub-pixel region and the transparent region on the first insulatinginterlayer, and may have the first refractive index.

In example embodiments, the planarization layer may have a first heightin the sub-pixel region, and the first height may extend in a directionthat is vertical to an upper surface of the substrate. The planarizationlayer may have a second height in the transparent region, and the secondheight may extending in the direction may be less than the first height.

In example embodiments, the pixel structure may include a firstelectrode, a light emitting layer, and a second electrode. The firstelectrode may be disposed on the first insulating interlayer. The lightemitting layer may be disposed on the first electrode. The secondelectrode may be disposed on the light emitting layer.

In example embodiments, the second electrode may be disposed in thesub-pixel region and the transparent region.

In example embodiments, the OLED device may further include a thin filmencapsulation structure. The thin film encapsulation structure may bedisposed on the pixel structure, and may include at least one a firstencapsulation layer and at least one a second encapsulation layer. Thefirst and second encapsulation layers may be alternately arranged.

In example embodiments, the first encapsulation layer may includeinorganic material(s) that have a refractive index in a range from 1.4to 1.6. The second encapsulation layer may include organic material(s)that have a refractive index in a range from 1.4 to 1.6.

In example embodiments, the first encapsulation layer may includesilicon oxynitride.

In example embodiments, the second electrode may be disposed in thesub-pixel region, and exposes the transparent region. The thin filmencapsulation structure may be in contact with the first insulatinginterlayer in the transparent region.

In example embodiments, the substrate may consist essentially of a glasssubstrate that has a refractive index in a range from 1.4 to 1.5.

In example embodiments, the buffer layer and the first gate insulationlayer may consist essentially of silicon oxide that has a refractiveindex in a range from 1.4 to 1.5.

In example embodiments, the active layer may consist essentially ofamorphous silicon or poly silicon.

In example embodiments, the first insulating interlayer may consistessentially of silicon oxynitride that has a refractive index in a rangefrom 1.7 to 1.8.

In example embodiments, the silicon oxynitride may consist essentiallyof silicon, oxygen, and nitrogen in a weight ratio of about 3.95:1:1.7.

In example embodiments, the OLED device may further include a secondgate insulation layer. The second gate insulation layer may beinterposed between the first gate insulation layer and the firstinsulating interlayer, may be disposed in the sub-pixel region and thetransparent region. The second gate insulation layer may consistessentially of silicon oxynitride that has a refractive index in a rangefrom 1.7 to 1.8.

In example embodiments, silicon oxynitride may consist essentially ofsilicon, oxygen, and nitrogen in a weight ratio of about 3.95:1:1.7.

In example embodiments, the OLED device may further include a secondelectrode. The second electrode may be interposed between the secondgate insulation layer and the first insulating interlayer, and may bedisposed on the second gate insulation layer under which the first gateelectrode is disposed.

In example embodiments, the OLED device may further include a secondinsulating interlayer. The second insulating interlayer may beinterposed between the first insulating interlayer and the source anddrain electrodes, and may be disposed in the sub-pixel region and thetransparent region. The second insulating interlayer may have the firstrefractive index. The second insulating interlayer may consistessentially of silicon oxide that has a refractive index in a range from1.4 to 1.5.

In example embodiments, the OLED device may further include a secondgate electrode. The second gate electrode may be interposed between thefirst insulating interlayer and the second insulating interlayer, andmay be disposed on the first insulating interlayer under which the firstgate electrode is disposed.

In example embodiments, the OLED device may further include aplanarization layer. The planarization layer may cover the source anddrain electrodes on the first insulating interlayer.

In example embodiments, the planarization layer may be disposed in thesub-pixel region on the first insulating interlayer, and may expose thetransparent region.

In example embodiments, the planarization layer may be disposed in thesub-pixel region and the transparent region on the first insulatinginterlayer, and may have the first refractive index.

In example embodiments, the planarization layer may have a first heightin the sub-pixel region, and the first height may extend in a directionthat is vertical to an upper surface of the substrate. The planarizationlayer may have a second height in the transparent region, and the secondheight extending in the direction may be less than the first height.

In example embodiments, the pixel structure may include a firstelectrode, a light emitting layer, and a second electrode. The firstelectrode may be disposed on the first insulating interlayer. The lightemitting layer may be disposed on the first electrode. The secondelectrode may be disposed on the light emitting layer.

In example embodiments, the second electrode may be disposed in thesub-pixel region and the transparent region.

An embodiment may be related to a display device, e.g., an organic lightemitting display device. The display device may include a light emittingelement (e.g., an organic light emitting element), a buffer layer, afirst gate insulation layer, and a switching element. A refractive indexof the first gate insulation layer may be equal to a refractive index ofthe buffer layer. The switching element may be electrically connected tothe light emitting element and may include an active layer, a first gateelectrode, a source electrode, and a drain electrode. The active layermay be positioned between the buffer layer and the first gate insulationlayer and may directly contact at least one of the buffer layer and thefirst gate insulation layer. The first gate insulation layer may bepositioned between the active layer and the first gate electrode and maydirectly contact at least one of the active layer and the first gateelectrode. Each of the source electrode and the drain electrode maydirectly contact the active layer.

The display device may include a pixel defining layer, which may have afirst opening. The active layer may be positioned between a firstportion of the buffer layer and a first portion of the first gateinsulation later in a direction perpendicular to a side (e.g., bottomside) of the buffer layer. A second portion of the first gate insulationlayer may be positioned between a second portion of the buffer layer andthe first opening in the direction perpendicular to a side of the bufferlayer.

The buffer layer may directly contact the first gate insulation layerand may include no nitride. A material of the buffer layer may beidentical to a material of the first gate insulation layer.

The refractive of the buffer layer may be greater than or equal to 1.4and may be less than or equal to 1.5.

The display device may include a first insulating interlayer. The firstgate electrode may be positioned between the first gate insulation layerand the first insulating interlayer. A refractive index of the firstinsulating interlayer may be greater than the refractive index of thefirst gate insulation layer.

A difference between the refractive index of the first insulatinginterlayer and the refractive index of the first gate insulation layermay be greater than or equal to 0.2 and may be less than or equal to0.4.

The refractive index of the first insulating interlayer may be greaterthan or equal to 1.7 and may be less than or equal to 1.8.

The first insulating interlayer may directly contact each of the firstgate electrode and the first gate insulation layer.

The display device may include a second gate insulation layer, which maydirectly contact the first insulating interlayer and may be positionedbetween the first gate electrode and the first insulating interlayer. Arefractive index of the second gate insulation layer may be equal to therefractive index of the first insulating interlayer.

The display device may include a pixel defining layer, which may have afirst opening. A first portion of the second gate insulation layer maybe positioned between the first gate electrode and a first portion ofthe first insulating interlayer in a direction perpendicular to a sideof the buffer layer and may directly contact the first portion of thefirst insulating interlayer. A second portion of the first insulatinginter layer may be positioned between a second portion of the secondgate insulation layer and the first opening in the directionperpendicular to the side of the buffer layer.

The display device may include a second gate electrode, which may bepositioned between the second gate insulation layer and the firstinsulating interlayer and may directly contact at least one of thesecond gate insulation layer and the first insulating interlayer.

The display device may include a second insulating interlayer. The firstinsulating interlayer may be positioned between the first gate electrodeand the second insulating interlayer and may directly contact the secondinsulating interlayer. A refractive index of the second insulatinginterlayer may be less than the refractive index of the first insulatinginterlayer.

A difference between the refractive index of the first insulatinginterlayer and the refractive index of the second insulating interlayermay be greater than or equal to 0.2 and may be less than or equal to0.4.

The refractive index of the second insulating interlayer may be equal tothe refractive index of the buffer layer.

The display device may include a second gate electrode, which may bepositioned between the first insulating interlayer and the secondinsulating interlayer and may directly contact at least one of the firstinsulating interlayer and the second insulating interlayer.

The display device may include: a transparent substrate. A refractiveindex of the transparent substrate may be equal to the refractive indexof the first insulating interlayer or the refractive index of the bufferlayer.

The display device may include a transparent polyimide layer and abarrier layer. The barrier layer may be positioned between thetransparent polyimide layer and the buffer layer. The buffer layer maybe positioned between the barrier layer and the active layer. Arefractive index of the barrier layer may be equal to the refractiveindex of the first insulating interlayer.

A material of the barrier layer may be identical to a material of thefirst insulating interlayer. A weight proportion of silicon, oxygen, andnitrogen of the material of the barrier layer may be 3.95:1:1.7.

The display device may include an encapsulation layer. A refractiveindex of the encapsulation layer may be equal to the refractive index ofthe first insulating interlayer or the refractive index of the bufferlayer. The light emitting element may be positioned between the firstinsulating interlayer and the encapsulation layer.

The display device may include an inorganic material layer and anorganic material layer. A refractive index of the inorganic materiallayer may be equal to the refractive index of the first insulatinginterlayer or the refractive index of the buffer layer. The organicmaterial layer may directly contact the inorganic layer. A refractiveindex of the inorganic material layer may be equal to the refractiveindex of the first insulating interlayer or the refractive index of thebuffer layer. One of the inorganic material layer and the organic layermay directly contact the first insulating interlayer and may bepositioned between the light emitting element and another one of theinorganic material layer and the organic layer.

In a display device (e.g., an OLED device) according to embodiments,refractive indexes of immediately neighboring insulation layers may besubstantially equal. Advantageously, the transmittance of a transparentregion of the display device may be satisfactory. In embodiments, adisplay device (e.g., an OLED device) includes one or more insulationlayers that enable desirable interface characteristics of an activelayer in a switching element of the display device. Advantageously,electron mobility in the switching element may be satisfactory, suchthat performance of the display device may be satisfactory.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating a display device, e.g., an organiclight emitting display (OLED) device, in accordance with exampleembodiments.

FIG. 2A is a cross-sectional view taken along a line I-I′ indicated inFIG. 1.

FIG. 2B is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 3 and FIG. 4 are graphs illustrating an average transmittance ofthe OLED device of FIG. 1 and an average transmittance of a comparativeexample.

FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9, and FIG. 10 are cross-sectionalviews illustrating a method of manufacturing a display device inaccordance with example embodiments.

FIG. 11 is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 12 is a cross-sectional view illustrating an OLED device.

FIG. 13A is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 13B is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 14 and FIG. 15 are graphs illustrating an average transmittance ofthe OLED device of FIG. 13A and an average transmittance of acomparative example.

FIG. 16A is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 16B is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 17 is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 18A is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 18B is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 19A is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 19B is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 20A is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 20B is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 21 is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 22 is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 23A is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 23B is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 24A is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 24B is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 25 is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

FIG. 26A is a cross-sectional view illustrating an OLED in accordancewith example embodiments.

FIG. 26B is a cross-sectional view illustrating an OLED device inaccordance with example embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments are explained with reference to the accompanying drawings.

Although the terms “first”, “second”, etc. may be used herein todescribe various elements, these elements should not be limited by theseterms. These terms may be used to distinguish one element from anotherelement. Thus, a first element discussed in this application may betermed a second element without departing from embodiments. Thedescription of an element as a “first” element may not require or implythe presence of a second element or other elements. The terms “first”,“second”, etc. may also be used herein to differentiate differentcategories or sets of elements. For conciseness, the terms “first”,“second”, etc. may represent “first-category (or first-set)”,“second-category (or second-set)”, etc., respectively.

If a first element (such as a layer, film, region, or substrate) isreferred to as being “on”, “neighboring”, “connected to”, or “coupledwith” a second element, then the first element can be directly on,directly neighboring, directly connected to, or directly coupled withthe second element, or an intervening element may also be presentbetween the first element and the second element. If a first element isreferred to as being “directly on”, “directly neighboring”, “directlyconnected to”, or “directed coupled with” a second element, then nointended intervening element (except environmental elements such as air)may be provided between the first element and the second element.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper”, and the like, may be used herein for ease of description todescribe one element or feature's spatial relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms may encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations), and the spatially relativedescriptors used herein should be interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to limit the embodiments. As usedherein, the singular forms, “a”, “an”, and “the” may indicate pluralforms as well, unless the context clearly indicates otherwise. The terms“includes” and/or “including”, when used in this specification, mayspecify the presence of stated features, integers, steps, operations,elements, and/or components, but may not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups.

Unless otherwise defined, terms (including technical and scientificterms) used herein have the same meanings as commonly understood by oneof ordinary skill in the art. Terms, such as those defined in commonlyused dictionaries, should be interpreted as having meanings that areconsistent with their meanings in the context of the relevant art andshould not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

The term “connect” may mean “electrically connect”, “directly connect”,or “indirectly connect”. The term “insulate” may mean “electricallyinsulate”. The term “conductive” may mean “electrically conductive”. Theterm “electrically connected” may mean “electrically connected withoutany intervening transistors”. If a component (e.g., a transistor) isdescribed as connected between a first element and a second element,then a source/drain/input/output terminal of the component may beelectrically connected to the first element through no interveningtransistors, and a drain/source/output/input terminal of the componentmay be electrically connected to the second element through nointervening transistors.

The term “conductor” may mean “electrically conductive member”. The term“insulator” may mean “electrically insulating member”. The term“dielectric” may mean “dielectric member”. The term “interconnect” maymean “interconnecting member”. The term “provide” may mean “provideand/or form”. The term “form” may mean “provide and/or form”.

Unless explicitly described to the contrary, the word “comprise” andvariations such as “comprises”, “comprising”, “include”, or “including”may imply the inclusion of stated elements but not the exclusion ofother elements.

FIG. 1 is a plan view illustrating a display device, e.g., an organiclight emitting display (OLED) device, in accordance with exampleembodiments.

Referring to FIG. 1, an organic light emitting display (OLED) device 100may include a plurality of pixel regions. One pixel region 10 among aplurality of pixel regions may include a first sub-pixel region 15, asecond sub-pixel region 20, and a third sub-pixel region 25 and atransparent region 30. For example, the pixel regions 10 may be arrangedin a first direction D1 and a second direction D2 on the entiresubstrate, which will be described below, included in the OLED device100. Here, the first direction D1 (e.g., a direction from thetransparent region 30 into the sub-pixel region 15) may be parallel toan upper surface of the substrate, and the second direction D2 may beperpendicular to the first direction D1.

The pixel regions 10 each may include the sub-pixel regions 15, 20, and25 and a transparent region 30. The sub-pixel regions 15, 20, and 25 anda transparent region 30 may be substantially surrounded by a pixeldefining layer 310. For example, the sub-pixel regions 15, 20, and 25and a transparent region 30 may be defined by the pixel defining layer310. That is, the pixel defining layer 310 may be disposed in one pixelregion 10 except the sub-pixel regions 15, 20, and 25 and a transparentregion 30.

First, second, and third sub-pixels may be disposed in the sub-pixelregions 15, 20, and 25, respectively. For example, the first sub-pixelmay emit a red color of a light, and the second sub-pixel may emit agreen color of a light. In addition, the third sub-pixel may emit a bluecolor of a light. The sub-pixels may be disposed at the same level onthe substrate.

In the transparent region 30, a light incident from the outside may betransmitted via the transparent region 30. An opening 275 may be locatedin the transparent region 30.

Since the OLED device 100 includes the transparent region 30, the OLEDdevice 100 may serve as a transparent OLED device capable oftransmitting a light incident from the outside.

In example embodiments, one pixel region 10 includes three sub-pixelregions and one transparent region, but not being limited thereto. Insome example embodiments, for example, a plurality of pixel regions maybe corresponding to one transparent region.

In example embodiments, an arrangement of a plurality of pixel regions10 is regularly arranged, but not being limited thereto. In some exampleembodiments, the pixel regions 10 may be irregularly arranged.

FIG. 2A is a cross-sectional view taken along a line I-I′ indicated inFIG. 1, and FIG. 2B is a cross-sectional view illustrating an OLEDdevice in accordance with example embodiments.

Referring to FIG. 2A, an organic light emitting display (OLED) device100 may include a substrate 110, a buffer layer 120, a semiconductorelement 250 (e.g., a switching element 250), a first gate insulationlayer 150, a second gate insulation layer 155, a pixel structure, afirst insulating interlayer 190, a planarization layer 270, a pixeldefining layer 310, a thin film encapsulation layer 450, etc. Thesubstrate 110 may include a polyimide layer 111 and a barrier layer 115.The pixel structure (e.g., light emitting element) may include mayinclude a first electrode 290, a light emitting layer 330 (e.g., anorganic light emitting layer), and a second electrode 340. The switchingelement 250 may include an active layer 130, a first gate electrode 170,a source electrode 210, and a drain electrode 230. The thin filmencapsulation layer 450 may include first encapsulation layers 451, 453,and 455 and second encapsulation layers 452 and 454.

As described above, the OLED device 100 may include a plurality of pixelregions. One pixel region among a plurality of pixel regions may have asub-pixel region 15 (e.g., a first sub-pixel region of FIG. 1) and atransparent region 30.

The switching element 250, the first electrode 290, the light emittinglayer 330, etc. may be disposed in the sub-pixel region 15. Theinsulation layers, etc. may be disposed in the transparent region 30.Meanwhile, the second electrode 340 may be entirely disposed in thesub-pixel region 15 and the transparent region 30.

A display image may be displayed in the sub-pixel region 15, and anobject (or a target) that is located in the back (or the rear) of theOLED display device 100 may be visible in the transparent region 30. Asthe OLED display device 100 includes the transparent region 30, the OLEDdisplay device 100 may serve as a transparent OLED device 100.

The substrate 110 may include transparent insulation material(s). Inexample embodiments, the substrate 110 may essentially include atransparent polyimide substrate. The transparent polyimide substrate maybe formed of a flexible transparent resin substrate. In this case, thetransparent polyimide substrate may include the polyimide layer 111 andthe barrier layer 115. For example, the transparent polyimide substratemay have a structure that the polyimide layer 111 and the barrier layer115 are stacked on a rigid glass substrate. In a manufacturing the OLEDdevice 100, after the buffer layer 120 is disposed on the barrier layer115 of the transparent polyimide substrate, the semiconductor element250 and the pixel structure may be disposed on the buffer layer 120.After the semiconductor element 250 and the pixel structure are formed,the rigid glass substrate may be removed. It may be difficult todirectly form the semiconductor element 250 and the pixel structure onthe transparent polyimide substrate because the transparent polyimidesubstrate is relatively thin and flexible. In embodiments, thesemiconductor element 250 and the pixel structure are formed on thetransparent polyimide substrate using the rigid glass substrate, andthen the transparent polyimide substrate including the polyimide layer111 and the barrier layer 115 may serve as the substrate 110 of the OLEDdevice 100 after the removal of the rigid glass substrate. As the OLEDdevice 100 includes the sub-pixel region 15 and the transparent region30, the substrate 110 may also include the sub-pixel region 15 and thetransparent region 30.

In example embodiments, a refractive index of the polyimide layer 111may be in a range from about 1.7 to about 1.8. The polyimide layer 111may include random copolymer or block copolymer. In addition, thepolyimide layer 111 may have a high transparency, a low coefficient ofthermal expansion, and a high glass transition temperature. Since thepolyimide layer 111 includes an imide radical, a heat resistance, achemical resistance, a wear resistance, and an electricalcharacteristics may be excellent.

The barrier layer 115 may include organic material(s) or inorganicmaterial(s) that have a refractive index in a range from about 1.7 toabout 1.8. The organic material(s) may include one or more of aphotoresist, a polyacryl-based resin, a polyimide-based resin, apolyamide-based resin, a siloxane-based resin, an acryl-based resin, anepoxy-based resin, etc. In addition, the inorganic material(s) mayinclude one or more of silicon compound, metal oxide, etc. For example,the barrier layer 115 may include one or more of silicon oxide (SiOx),silicon nitride (SiNx), silicon oxynitride (SiOxNy), silicon oxycarbide(SiOxCy), silicon carbon nitride (SiCxNy), aluminum oxide (AlOx),aluminum nitride (AlNx), tantalum oxide (TaOx), hafnium oxide (HfOx),zirconium oxide (ZrOx), titanium oxide (TiOx), etc. In exampleembodiments, the barrier layer 115 may consist essentially of SiOxNythat has a refractive index from about 1.7 to about 1.8. In embodiments,the barrier layer 115 may have a substantially single composition ofSiOxNy. The barrier layer 115 may block moisture or water capable ofbeing permeated via the polyimide layer 111. In embodiments, thepolyimide layer 111 and the barrier layer 115 may have substantially thesame refractive index (value). For example, SiOxNy may consistessentially of silicon, oxygen, and nitrogen in a respective weightratio of about 3.95:1:1.7. That is, SiOxNy may be formed controlling theweight ratio such that a refractive index of SiOxNy has a refractiveindex in a range from about 1.7 to about 1.8. In an embodiment, SiOxNymay consist essentially of silicon, oxygen, and nitrogen in a weightratio of about 2.5:1:0.88.

In some example embodiments, the substrate 110 may include a quartzsubstrate, a synthetic quartz substrate, a calcium fluoride substrate, afluoride-doping quartz substrate, a soda lime substrate, a non-alkalisubstrate etc.

The buffer layer 120 may be disposed on the substrate 110. The bufferlayer 120 may include organic material(s) or inorganic material(s) thathave a refractive index in a range from about 1.4 to about 1.5 (e.g., afirst refractive index). In example embodiments, the buffer layer 120may consist essentially of SiOx that has a refractive index from about1.4 to about 1.5. In embodiments, the buffer layer 120 may have asubstantially single composition of SiOx. The buffer layer 120 may bedisposed on the entire substrate 110. The buffer layer 120 may preventthe diffusion of metal atoms and/or impurities from the substrate 110into the switching element 250 and the pixel structure. Additionally,the buffer layer 120 may control a rate of a heat transfer in acrystallization process for forming the active layer 130, therebyobtaining a substantially uniform active layer 130. Furthermore, thebuffer layer 120 may improve a surface flatness of the substrate 110when a surface of the substrate 110 is relatively irregular. Further, asthe buffer layer 120 is disposed on the substrate 110, the stressgenerated from the pixel structure formed on the substrate 110 may bereduced. A type of the substrate 110, at least two buffer layers may beprovided on the substrate 110.

The switching element 250 may include the active layer 130, the firstgate electrode 170, the source electrode 210, and the drain electrode230, and may be disposed in the sub-pixel region 15 on the substrate110.

The active layer 130 may be disposed in the sub-pixel region 15 on thesubstrate 110. For example, the active layer 130 may include an oxidesemiconductor, an inorganic semiconductor (e.g., amorphous silicon,polysilicon, etc.), an organic semiconductor, etc. In exampleembodiments, the active layer 130 may consist essentially of amorphoussilicon or polysilicon. A lower surface of the active layer 130 may bein contact with the buffer layer 120, and an upper surface of the activelayer 130 may be in contact with the first gate insulation layer 150.

The first gate insulation layer 150 may be disposed on the active layer130. The first gate insulation layer 150 may include organic material(s)or inorganic material(s) that have a refractive index in a range fromabout 1.4 to about 1.5. In example embodiments, the first gateinsulation layer 150 may consist essentially of SiOx that has arefractive index from about 1.4 to about 1.5. In embodiments, the firstgate insulation layer 150 may have a substantially single composition ofSiOx. In addition, the buffer layer 120 and the first gate insulationlayer 150 may have substantially the same refractive index (value). Thefirst gate insulation layer 150 may extend in a first direction D1(e.g., a direction that is from the transparent region 30 into thesub-pixel region 15) on the buffer layer 120. The first direction D1 maybe parallel to an upper surface of the substrate 110. The first gateinsulation layer 150 may cover the active layer 130 in the sub-pixelregion 15, and may be disposed on the entire buffer layer 120. Forexample, the first gate insulation layer 150 may sufficiently cover theactive layer 130, and may have a substantially even surface without astep around the active layer 130. In an embodiment, the first gateinsulation layer 150 may cover the active layer 130, and may be disposedas a substantially uniform thickness along a profile of the active layer130. In example embodiments, interface characteristics of the activelayer 130 may be increased because an upper surface of the active layer130 including amorphous silicon or polysilicon is in contact with thefirst gate insulation layer 150 including SiOx and a lower surface ofthe active layer 130 including amorphous silicon or polysilicon is incontact with the buffer layer 120 including SiOx. Meanwhile, when anitride-based insulation layer is in contact with a silicon-based activelayer 130, interface characteristics may be reduced. In exampleembodiments, an insulation layer including SiNx or SiOxNy may not be indirect contact with the active layer 130 in the OLED device 100.Accordingly, desirable interface characteristics of the active layer 130may be attained, and performance of the switching element 250 includedin the OLED device 100 may be satisfactory.

The first gate electrode 170 may be disposed on the first gateinsulation layer 150. The first gate electrode 170 may be disposed onthe first gate insulation layer 150 under which the active layer 130 isdisposed. The first gate electrode 170 may include a metal, a metalalloy, metal nitride, conductive metal oxide, transparent conductivematerial(s), etc. For example, the first gate electrode 170 may includegold (Au), silver (Ag), aluminum (Al), platinum (Pt), nickel (Ni),titanium (Ti), palladium (Pd), magnesium (Mg), Calcium (Ca), Lithium(Li), chrome (Cr), tantalum (Ta), tungsten (W), copper (Cu), molybdenum(Mo), scandium (Sc), neodymium (Nd), Iridium (Ir), an alloy of aluminum,aluminum nitride (AlNx), an alloy of silver, tungsten nitride (WNx), analloy of copper, an alloy of molybdenum, titanium nitride (TiNx), chromenitride (CrNx), tantalum nitride (TaNx), strontium ruthenium oxide(SRO), zinc oxide (ZnOx), indium tin oxide (ITO), stannum oxide (SnOx),indium oxide (InOx), gallium oxide (GaOx), indium zinc oxide (IZO), etc.These may be used alone or in a suitable combination thereof. In anembodiment, the first gate electrode 170 may have a multilayerstructure.

The second gate insulation layer 155 may be disposed on the first gateelectrode 170. The second gate insulation layer 155 may include organicmaterial(s) or inorganic material(s) that have a refractive index in arange from about 1.7 to about 1.8 (e.g., a second refractive index). Inexample embodiments, the second gate insulation layer 155 may consistessentially of SiOxNy that has a refractive index in a range from 1.7 to1.8. In embodiments, the second gate insulation layer 155 may have asubstantially single composition of SiOxNy. For example, SiOxNy mayconsist essentially of silicon, oxygen, and nitrogen in a weight ratioof about 3.95:1:1.7. That is, SiOxNy may be formed controlling theweight ratio such that a refractive index of SiOxNy has a refractiveindex in a range from 1.7 to 1.8. In an embodiment, SiOxNy may consistessentially of silicon, oxygen, and nitrogen in a weight ratio of about2.5:1:0.88. In addition, the substrate 110 and the second gateinsulation layer 155 may have substantially the same refractive index(value). As the second gate insulation layer 155 including SiOxNy isspaced from the active layer 130, desirable interface characteristics ofthe active layer 130 may be attained. For example, hydrogen may beinjected in a process annealing the active layer 130. The hydrogen maycombine with a dangling bond of the active layer 130. The second gateinsulation layer 155 may support the hydrogen combination process.Accordingly, desirable interface characteristics of the active layer 130may be attained, and a mean free path of electrons included in theactive layer 130 may be desirable. That is, mobility of electron may beenhanced, and characteristics of the switching element 250 included inthe OLED device 100 may be improved. The second gate insulation layer155 may extend in the first direction D1 on the substrate 110. Thesecond gate insulation layer 155 may cover the first gate electrode 170in the sub-pixel region 15, and may be disposed on the entire first gateinsulation layer 150. For example, the second gate insulation layer 155may sufficiently cover the first gate electrode 170, and may have asubstantially even surface without a step around the first gateelectrode 170. In an embodiment, the second gate insulation layer 155may cover the first gate electrode 170, and may be disposed as asubstantially uniform thickness along a profile of the first gateelectrode 170.

The first insulating interlayer 190 may be disposed on the second gateinsulation layer 155. The first insulating interlayer 190 may includeorganic material(s) or inorganic material(s) that have a refractiveindex in a range from about 1.7 to about 1.8 (e.g., a second refractiveindex). In example embodiments, the first insulating interlayer 190 mayconsist essentially of SiOxNy that has a refractive index in a rangefrom 1.7 to 1.8. For example, SiOxNy may consist essentially of silicon,oxygen, and nitrogen in a weight ratio of about 3.95:1:1.7. That is,SiOxNy may be formed controlling the weight ratio such that a refractiveindex of SiOxNy has a refractive index in a range from 1.7 to 1.8. In anembodiment, SiOxNy may consist essentially of silicon, oxygen, andnitrogen in a weight ratio of about 2.5:1:0.88. In embodiments, thefirst insulating interlayer 190 may have a substantially singlecomposition of SiOxNy. In addition, the first insulating interlayer 190,the substrate 110 and the second gate insulation layer 155 may havesubstantially the same refractive index (value). In embodiments, as thesubstrate 110, the second gate insulation layer 155, and the firstinsulating interlayer 190 have substantially the same refractive index(value), a transmittance in the transparent region 30 of the OLED device100 may be increased. The first insulating interlayer 190 may extend inthe first direction D1 on the second gate insulation layer 155.

In some example embodiments, as illustrated in FIG. 2B, the first gateinsulation layer 150 may be disposed on the active layer 130, and thesecond gate insulation layer 155 may be disposed on the first gateinsulation layer 150. In addition, the first gate electrode 170 may bedisposed on the second gate insulation layer 155. That is, the first andsecond gate insulation layer 150 and 155 may be interposed between thebuffer 120 and the gate electrode 170. Here, the first gate insulationlayer 150 may consist essentially of SiOx that has a refractive indexfrom about 1.4 to about 1.5, and the first gate electrode 170 mayinclude a metal, a metal alloy, metal nitride, conductive metal oxide,transparent conductive material(s), etc. In addition, the second gateinsulation layer 155 may consist essentially of SiOxNy that has arefractive index in a range from 1.7 to 1.8, and SiOxNy may consistessentially of silicon, oxygen, and nitrogen in a weight ratio of about2.5:1:0.88. The first insulating interlayer 190 may be disposed on thesecond gate insulation layer 155 and the first gate electrode 170. Thefirst insulating interlayer 190 may consist essentially of SiOxNy thathas a refractive index in a range from 1.7 to 1.8, and SiOxNy mayconsist essentially of silicon, oxygen, and nitrogen in a weight ratioof about 2.5:1:0.88.

Referring again to FIG. 2, the source electrode 210 and the drainelectrode 230 may be disposed on the first insulating interlayer 190.The source electrode 210 may be in contact with a first side (e.g., asource region) of the active layer 130 via a contact hole formed byremoving a portion of the first insulating interlayer 190, the secondgate insulation layer 155, and the first gate insulation layer 150 each.The drain electrode 230 may be in contact with a second side (e.g., adrain region) of the active layer 130 via a contact hole formed byremoving a portion of the first insulating interlayer 190, the secondgate insulation layer 155, and the first gate insulation layer 150 each.Each of the source electrode 210 and the drain electrode 230 may includea metal, an alloy, metal nitride, conductive metal oxide, transparentconductive material(s), etc. These may be used alone or in a suitablecombination thereof. In embodiments, the switching element 250 mayinclude the active layer 130, the first gate electrode 170, the sourceelectrode 210, and the drain electrode 230.

The planarization layer 270 may be disposed on the source electrode 210and the drain electrode 230. The planarization layer 270 may extend inthe first direction D1 on the first insulating interlayer 190. Theplanarization layer 270 may have an opening 275 exposing the firstinsulating interlayer 190 in the transparent region 30, and may coverthe source electrode 210 and the drain electrode 230 in the sub-pixelregion 15. For example, the planarization layer 270 may be disposed as arelatively high thickness to sufficiently cover the source electrode 210and the drain electrode 230. In this case, the planarization layer 270may have a substantially even upper surface, and a planarization processmay be further performed on the planarization layer 270 to implement theeven upper surface of the planarization layer 270. In an embodiment, theplanarization layer 270 may cover the source electrode 210 and the drainelectrode 230, and may be disposed as a substantially uniform thicknessalong a profile of the source electrode 210 and the drain electrode 230.The planarization layer 270 may include organic material(s) or inorganicmaterial(s).

The first electrode 290 may be disposed in the sub-pixel region 15 onthe planarization layer 270. The first electrode 290 may be in contactwith the drain electrode 230 via a contact hole formed by removing aportion of the planarization layer 270. In addition, the first electrode290 may be electrically connected to the switching element 250. Thefirst electrode 290 may include a metal, a metal alloy, metal nitride,conductive metal oxide, transparent conductive material(s), etc. Thesemay be used alone or in a suitable combination thereof.

The pixel defining layer 310 may expose at least a portion of the firstelectrode 290, and then may be disposed on the planarization layer 270.For example, the pixel defining layer 310 may cover both lateralportions of the first electrode 290, and may expose the opening 275 ofthe planarization layer 270. In this case, the light emitting layer 330may be disposed on the first electrode 290 exposed by the pixel defininglayer 310. The pixel defining layer 310 may include inorganicmaterial(s) or organic material(s).

The light emitting layer 330 may be disposed on a portion of the firstelectrode 290 that is exposed by the pixel defining layer 310. The lightemitting layer 330 may have a multi-layered structure including anemission layer (EL), a hole injection layer (HIL), a hole transfer layer(HTL), an electron transfer layer (ETL), an electron injection layer(EIL), etc. The EL of the light emitting layer 330 may be formed usingat least one of light emitting material(s) capable of generatingdifferent colors of light (e.g., a red color of light, a blue color oflight, and a green color of light, etc.) according to first, second, andthird sub-pixels illustrated in FIG. 1. In an embodiment, the EL of thelight emitting layer 330 may generally generate a white color of lightby stacking a plurality of light emitting material(s) capable ofgenerating different colors of light such as a red color of light, agreen color of light, a blue color of light, etc. In some exampleembodiments, the HIL, the HTL, the ETL, the EIL, etc. except the EL maybe disposed in the transparent region 30 on the first insulatinginterlayer 190.

The second electrode 340 may be disposed on the pixel defining layer310, the light emitting layer 330, a portion of the planarization layer270, and a portion of the first insulating interlayer 190. The secondelectrode 340 may cover the pixel defining layer 310, the firstinsulating interlayer 190, the planarization layer 270, and the lightemitting layer 330 in the sub-pixel region 15 and the transparent region30. The second electrode 340 may include a metal, a metal alloy, metalnitride, conductive metal oxide, transparent conductive material(s),etc.

The thin film encapsulation structure 450 may be disposed on the secondelectrode 340. The thin film encapsulation structure 450 may include atleast one first encapsulation layer and at least one secondencapsulation layer. For example, the second encapsulation layer 452 maybe disposed on the first encapsulation layer 451. The firstencapsulation layers 451, 453, and 455 and the second encapsulationlayers 452 and 454 may be alternately and repeatedly arranged. The firstencapsulation layer 451 may cover the second electrode 340, and may bedisposed as a substantially uniform thickness along a profile of thesecond electrode 340. The first encapsulation layer 451 may prevent thepixel structure form being deteriorated by the permeation of moisture,water, oxygen, etc. In addition, the first encapsulation layer 451 mayprotect the pixel structure from external impacts. The firstencapsulation layer 451 may include inorganic material(s). In anembodiment, the first encapsulation layer 451 may include SiOxNy.

The second encapsulation layer 452 may be disposed on the firstencapsulation layer 451. The second encapsulation layer 452 may improvea surface flatness of the OLED device 100, and may protect the pixelstructure disposed in the sub-pixel region 15. The second encapsulationlayer 452 may include organic material(s).

The first encapsulation layer 453 may be disposed on the secondencapsulation layer 452. The first encapsulation layer 453 may cover thesecond encapsulation layer 452, and may be disposed as a substantiallyuniform thickness along a profile of the second encapsulation layer 452.The first encapsulation layer 453 together with the first encapsulationlayer 451 and the second encapsulation layer 452 may prevent the pixelstructure form being deteriorated by the permeation of moisture, water,oxygen, etc. In addition, the first encapsulation layer 453 togetherwith the first encapsulation layer 451 and the second encapsulationlayer 452 may protect the pixel structure from external impacts. Thefirst encapsulation layer 453 may include inorganic material(s). In anembodiment, the first encapsulation layer 453 may include SiOxNy.

The second encapsulation layer 454 may be disposed on the firstencapsulation layer 453. The second encapsulation layer 454 may performfunctions substantially the same as or similar to those of the secondencapsulation layer 452, and the second encapsulation layer 454 mayinclude a material substantially the same as or similar to that of thesecond encapsulation layer 452. The first encapsulation layer 455 may bedisposed on the second encapsulation layer 454. The first encapsulationlayer 455 may perform functions substantially the same as or similar tothose of the first encapsulation layers 451 and 453, and the firstencapsulation layer 455 may include a material substantially the same asor similar to that of the first encapsulation layers 451 and 453. Insome example embodiments, the thin film encapsulation structure 450 mayhave three layers structure having the first encapsulation layer 451,the second encapsulation layer 452, and the first encapsulation layer453 or seven layers structure having the first encapsulation layer 451,the second encapsulation layer 452, the first encapsulation layer 453,the second encapsulation layer 454, the first encapsulation layer 455,an extra first encapsulation layer, and an extra second encapsulationlayer. In an embodiment, the thin film encapsulation structure 450 mayinclude organic material(s) or inorganic material(s) that have arefractive index in a range from 1.7 to 1.8. In some exampleembodiments, the thin film encapsulation structure 450 and the substrate110 may include substantially the same material(s). For example, thethin film encapsulation structure 450 may include a quartz substrate, asynthetic quartz substrate, a calcium fluoride substrate, afluoride-doping quartz substrate, a soda lime substrate, a non-alkalisubstrate etc.

As the OLED device 100 in accordance with example embodiments includesthe second gate insulation layer 155 and the first insulating interlayer190 that have substantially the same refractive index as the substrate110, a transmittance of the transparent region 30 may be increased. Inaddition, as the active layer 130 is interposed between the buffer layer120 and the first gate insulation layer 150 that have SiOx, interface ofthe active layer 130 may be improved. In embodiments, the OLED device100 may serve as a flexible transparent OLED device that has arelatively high transmittance and has an effective switching element250.

FIGS. 3 and 4 are graphs illustrating an average transmittance of theOLED device of FIG. 1 and an average transmittance of a comparativeexample.

The following Examples and Comparative Examples are provided in order tohighlight characteristics of one or more embodiments, but it will beunderstood that the Examples and Comparative Examples are not to beconstrued as limiting the scope of the embodiments, nor are theComparative Examples to be construed as being outside the scope of theembodiments. Further, it will be understood that the embodiments are notlimited to the particular details described in the Examples andComparative Examples.

Experimental Example: Evaluation on Transmittances Varying InsulationLayer Structures

A barrier layer, a buffer layer, a first gate insulation layer, a secondgate insulation layer, and a first insulating interlayer, each of whichincluded stacked silicon oxide layer and silicon nitride layer weresequentially formed on a polyimide substrate having a thickness of 10micrometers to obtain stacked structures of Comparative Example (referto FIG. 3).

A barrier layer having a single composition of silicon oxynitride, abuffer layer having a single composition of silicon oxide, a first gateinsulation layer having a single composition of silicon oxide, a secondgate insulation layer having a single composition of silicon oxynitride,and a first insulating interlayer having a single composition of siliconoxynitride were sequentially formed on the polyimide substrate to obtaina stacked structure of Example (refer to FIG. 2).

Specific structures of Comparative Example and Example are shown inTable 1 below. In Table 1, the silicon oxide layer, the silicon nitridelayer, and a silicon oxynitride layer are abbreviated as an oxide, anitride, and an oxynitride, respectively.

TABLE 1 Fist Gate Insulation Layer/ First Insulating Barrier LayerBuffer Layer Second Gate Insulation Layer Interlayer Comparative oxide(1,500 Å)/ nitride (1,000 Å)/ oxide (750 Å)/ oxide (3,000 Å)/ Example(FIG. 3) nitride (600 Å)/ oxide (3,000 Å) nitride (400 Å) nitride (2,000Å) oxide (1,500 Å)/ nitride (600 Å)/ oxide (1,500 Å) Example (FIG. 2)oxynitride oxide oxide (3000 Å)/ oxynitride (5,600 Å) (3,000 Å)oxynitride (400 Å) (5,000 Å)

A light was irradiated over each stacked structures of ComparativeExample and Example, and transmittances were measured. The measuredvalues are shown in Table 2 below.

TABLE 2 Comparative Example (FIG. 3) Example (FIG. 2) Average 64.6% 83%Transmittance

As shown in Table 2, when the stacked structure having a barrier layerhaving a single composition of silicon oxynitride, a buffer layer havinga single composition of silicon oxide, a first gate insulation layerhaving a single composition of silicon oxide, a second gate insulationlayer having a single composition of silicon oxynitride, and a firstinsulating interlayer having a single composition of silicon oxynitridewas formed, the transmittance was drastically increased compared tothose measured in Comparative Example, having repeatedly stackeddifferent insulation layers.

FIGS. 5, 6, 7, 8, 9, and 10 are cross-sectional views illustrating amethod of manufacturing a display device in accordance with exampleembodiments.

Referring to FIG. 5, a substrate 510 including transparent insulationmaterial(s) may be provided. In example embodiments, the substrate 510may consist essentially of transparent polyimide substrate. Thetransparent polyimide substrate may be formed using a flexibletransparent resin substrate. In this case, the transparent polyimidesubstrate may include a polyimide layer 511 and a barrier layer 515. Forexample, the transparent polyimide substrate may have a structure thatthe polyimide layer 511 and the barrier layer 515 are stacked on a rigidglass substrate. In a manufacturing an OLED device, after a buffer layer520 is formed on the barrier layer 515 of the transparent polyimidesubstrate, a semiconductor element (e.g., switching element) and a pixelstructure may be formed on the buffer layer 520. After the semiconductorelement and the pixel structure are formed, the rigid glass substratemay be removed. It may be difficult to directly form the semiconductorelement and the pixel structure on the transparent polyimide substratebecause the transparent polyimide substrate is relatively thin andflexible. In embodiments, the semiconductor element and the pixelstructure are formed on the transparent polyimide substrate using therigid glass substrate, and then the transparent polyimide substrateincluding the polyimide layer 511 and the barrier layer 515 may serve asthe substrate 510 of the OLED device after the removal of the rigidglass substrate. As the OLED device includes a sub-pixel region 15 and atransparent region 30, the substrate 510 may also include the sub-pixelregion 15 and the transparent region 30.

In example embodiments, a refractive index of the polyimide layer 511may be in a range from 1.7 to 1.8. The polyimide layer 511 may be formedusing random copolymer or block copolymer. In addition, the polyimidelayer 511 may have a high transparency, a low coefficient of thermalexpansion, and a high glass transition temperature. Since the polyimidelayer 511 includes an imide radical, a heat resistance, a chemicalresistance, a wear resistance, and an electrical characteristics may beexcellent.

The barrier layer 515 may consist essentially of SiOxNy that has arefractive index in a range from 1.7 to 1.8. For example, SiOxNy mayconsist essentially of silicon, oxygen, and nitrogen in a weight ratioof about 3.95:1:1.7. That is, SiOxNy may be formed controlling theweight ratio such that a refractive index of SiOxNy has a refractiveindex in a range from 1.7 to 1.8. In an embodiment, SiOxNy may consistessentially of silicon, oxygen, and nitrogen in a weight ratio of about2.5:1:0.88. In embodiments, the barrier layer 515 may have asubstantially single composition of SiOxNy. The barrier layer 115 mayblock moisture or water capable of being permeated via the polyimidelayer 511. In this way, the polyimide layer 511 and the barrier layer515 may have substantially the same refractive index (value).

The buffer layer 520 may be formed on the substrate 510. The bufferlayer 520 may consist essentially of SiOx that has a refractive index ina range from 1.4 to 1.5. In embodiments, the buffer layer 520 may have asubstantially single composition of SiOx. The buffer layer 520 may beformed on the entire substrate 510. The buffer layer 520 may prevent thediffusion of metal atoms and/or impurities from the substrate 510 into aswitching element and a pixel structure. Additionally, the buffer layer520 may control a rate of a heat transfer in a crystallization processfor forming an active layer 530, thereby obtaining a substantiallyuniform active layer 530. Furthermore, the buffer layer 520 may improvea surface flatness of the substrate 510 when a surface of the substrate510 is relatively irregular. Further, as the buffer layer 520 is formedon the substrate 510, the stress generated from the pixel structureformed on the substrate 510 may be reduced.

The active layer 530 may be formed in the sub-pixel region 15 on thebuffer layer 520. The active layer 530 may be formed using amorphoussilicon or polysilicon.

A first gate insulation layer 550 may be formed on the active layer 530.The first gate insulation layer 550 may consist essentially of SiOx thathas a refractive index in a range from 1.4 to 1.5. In embodiments, thefirst gate insulation layer 550 may have a substantially singlecomposition of SiOx. In addition, the buffer layer 520 and the firstgate insulation layer 550 may have substantially the same refractiveindex (value). The first gate insulation layer 550 may extend in a firstdirection D1 (e.g., a direction that is parallel to an upper surface ofthe substrate 510) on the buffer layer 520. The first gate insulationlayer 550 may cover the active layer 530 in the sub-pixel region 15, andmay be formed on the entire buffer layer 520. For example, the firstgate insulation layer 550 may sufficiently cover the active layer 530,and may have a substantially even surface without a step around theactive layer 530. In an embodiment, the first gate insulation layer 550may cover the active layer 530, and may be formed as a substantiallyuniform thickness along a profile of the active layer 530. In exampleembodiments, interface characteristics of the active layer 530 may beincreased because an upper surface of the active layer 530 includingamorphous silicon or polysilicon is in contact with the first gateinsulation layer 550 including SiOx and a lower surface of the activelayer 130 including amorphous silicon or polysilicon is in contact withthe buffer layer 520 including SiOx.

Referring to FIG. 6, a first gate electrode 570 may be formed the firstgate insulation layer 550 under which the active layer 530 is located.The first gate electrode 570 may be formed using a metal, a metal alloy,metal nitride, conductive metal oxide, transparent conductivematerial(s), etc. For example, the first gate electrode 570 may includeone or more of Au, Ag, Al, Pt, Ni, Ti, Pd, Mg, Ca, Li, Cr, Ta, W, Cu,Mo, Sc, Nd, Ir, an alloy of aluminum, AlNx, an alloy of silver, WNx, analloy of copper, an alloy of molybdenum, TiNx, CrNx, TaNx, SRO, ZnOx,ITO, SnOx, InOx, GaOx, IZO, etc. These may be used alone or in asuitable combination thereof.

A second gate insulation layer 555 may be formed on the first gateelectrode 570. The second gate insulation layer 555 may include consistessentially of SiOxNy that has a refractive index in a range from 1.7 to1.8. For example, SiOxNy may consist essentially of silicon, oxygen, andnitrogen in a weight ratio of about 3.95:1:1.7. That is, SiOxNy may beformed controlling the weight ratio such that a refractive index ofSiOxNy has a refractive index in a range from 1.7 to 1.8. In anembodiment, SiOxNy may consist essentially of silicon, oxygen, andnitrogen in a weight ratio of about 2.5:1:0.88. In embodiments, thesecond gate insulation layer 555 may have a substantially singlecomposition of SiOxNy.

In addition, the substrate 510 and the second gate insulation layer 555may have substantially the same refractive index (value). As the secondgate insulation layer 555 including SiOxNy is formed, desirableinterface characteristics of the active layer 530 may be attained. Forexample, hydrogen may be injected in a process annealing the activelayer 530. The hydrogen may combine with a dangling bond of the activelayer 530. The second gate insulation layer 555 may support the hydrogencombination process. Accordingly, desirable interface characteristics ofthe active layer 530 may be attained, and a mean free path of electronsincluded in the active layer 530 may be desirable. That is, mobility ofelectron may be enhanced. The second gate insulation layer 555 mayextend in the first direction D1 on the substrate 510. The second gateinsulation layer 555 may cover the first gate electrode 570 in thesub-pixel region 15, and may be formed on the entire first gateinsulation layer 550. For example, the second gate insulation layer 555may sufficiently cover the active layer 530, and may have asubstantially even surface without a step around the first gateelectrode 570. In an embodiment, the second gate insulation layer 555may cover the first gate electrode 570, and may be formed as asubstantially uniform thickness along a profile of the first gateelectrode 570.

Referring to FIG. 7, a first insulating interlayer 590 may be formed onthe second gate insulation layer 555. The first insulating interlayer590 may consist essentially of SiOxNy that has a refractive index in arange from 1.7 to 1.8. For example, SiOxNy may consist essentially ofsilicon, oxygen, and nitrogen in a weight ratio of about 3.95:1:1.7.That is, SiOxNy may be formed controlling the weight ratio such that arefractive index of SiOxNy has a refractive index in a range from 1.7 to1.8. Accordingly, the first insulating interlayer 590 may have asubstantially single composition of SiOxNy. In addition, the firstinsulating interlayer 590, the substrate 510 and the second gateinsulation layer 555 may have substantially the same refractive index(value). Accordingly, as the substrate 510, the second gate insulationlayer 555, and the first insulating interlayer 590 have substantiallythe same refractive index (value), a transmittance in the transparentregion 30 of the OLED device may be increased. The first insulatinginterlayer 590 may extend in the first direction D1 on the second gateinsulation layer 555.

A source electrode 610 and a drain electrode 630 may be formed on thefirst insulating interlayer 590. The source electrode 610 may be incontact with a source region of the active layer 530 perforating acontact hole formed by removing a portion of the first insulatinginterlayer 590, the second gate insulation layer 555, and the first gateinsulation layer 550 each. The drain electrode 630 may be in contactwith a drain region of the active layer 530 perforating a contact holeformed by removing a portion of the first insulating interlayer 590, thesecond gate insulation layer 555, and the first gate insulation layer550 each. Each of the source electrode 610 and the drain electrode 630may be formed using a metal, an alloy, metal nitride, conductive metaloxide, transparent conductive material(s), etc. These may be used aloneor in a suitable combination thereof. Accordingly, a switching element650 including the active layer 530, the first gate electrode 570, thesource electrode 610, and the drain electrode 630 may be formed.

A preliminary planarization layer 671 may be formed on the sourceelectrode 610 and the drain electrode 630. The preliminary planarizationlayer 671 may extend in the first direction D1 on the first insulatinginterlayer 590. The preliminary planarization layer 671 may cover thesource electrode 610 and the drain electrode 630 in the sub-pixel region15. For example, the preliminary planarization layer 671 may be formedas a relatively high thickness to sufficiently cover the sourceelectrode 610 and the drain electrode 630. In this case, the preliminaryplanarization layer 671 may have a substantially even upper surface, anda planarization process may be further performed on the preliminaryplanarization layer 671 to implement the even upper surface of thepreliminary planarization layer 671. The preliminary planarization layer671 may be formed using organic material(s) or inorganic material(s).

Referring to FIG. 8, a planarization layer 670 may be formed after anopening 275 exposing the first insulating interlayer 190 in thetransparent region 30 and a contact hole exposing the drain electrode630 in the sub-pixel region 15 are formed in the preliminaryplanarization layer 671.

The first electrode 690 may be formed in the sub-pixel region 15 on theplanarization layer 670. The first electrode 690 may be in contact withthe drain electrode 230 perforating the contact hole formed by removinga portion of the planarization layer 670. The first electrode 290 may beformed using a metal, a metal alloy, metal nitride, conductive metaloxide, transparent conductive material(s), etc. These may be used aloneor in a suitable combination thereof.

A pixel defining layer 710 may expose at least a portion of the firstelectrode 690, and then may be formed on the planarization layer 670.For example, the pixel defining layer 710 may cover both lateralportions of the first electrode 690, and may expose the opening 675 ofthe planarization layer 670. The pixel defining layer 710 may be formedusing inorganic material(s) or organic material(s).

Referring to FIG. 9, a light emitting layer 730 may be formed on aportion of the first electrode 690 that is exposed by the pixel defininglayer 710. The light emitting layer 730 may have a multi-layeredstructure including EL, HIL, HTL, ETL, EIL, etc. The EL of the lightemitting layer 730 may be formed using at least one of light emittingmaterial(s) capable of generating at least one of different colors oflight (e.g., a red color of light, a blue color of light, and a greencolor of light, etc.) according to first, second, and third sub-pixelsillustrated in FIG. 1. In an embodiment, the EL of the light emittinglayer 730 may generally generate a white color of light by stacking aplurality of light emitting material(s) capable of generating differentcolors of light such as a red color of light, a green color of light, ablue color of light, etc. In some example embodiments, the HIL, the HTL,the ETL, the EIL, etc. except the EL may be formed in the transparentregion 30 on the first insulating interlayer 590.

A second electrode 740 may be formed on the pixel defining layer 710,the light emitting layer 730, a portion of the planarization layer 670,and a portion of the first insulating interlayer 590. The secondelectrode 740 may cover the pixel defining layer 710, the firstinsulating interlayer 590, the planarization layer 670, and the lightemitting layer 730 in the sub-pixel region 15 and the transparent region30. The second electrode 740 may be formed using a metal, a metal alloy,metal nitride, conductive metal oxide, transparent conductivematerial(s), etc. Accordingly, the pixel structure may be formed.

Referring to FIG. 10, a thin film encapsulation structure 850 may beformed on the second electrode 740. The thin film encapsulationstructure 850 may include at least one first encapsulation layer and atleast one second encapsulation layer. For example, a secondencapsulation layer 852 may be formed on a first encapsulation layer851. The first encapsulation layers and the second encapsulation layersmay be alternately and repeatedly arranged. The first encapsulationlayer 851 may cover the second electrode 740, and may be formed as asubstantially uniform thickness along a profile of the second electrode740. The first encapsulation layer 851 may prevent the pixel structureform being deteriorated by the permeation of moisture, water, oxygen,etc. In addition, the first encapsulation layer 851 may protect thepixel structure from external impacts. The first encapsulation layer 851may be formed using inorganic material(s).

The second encapsulation layer 852 may be formed on the firstencapsulation layer 851. The second encapsulation layer 852 may improvea surface flatness of the OLED device, and may protect the pixelstructure formed in the sub-pixel region 15. The second encapsulationlayer 852 may be formed using organic material(s).

The first encapsulation layer 853 may be formed on the secondencapsulation layer 852. The first encapsulation layer 853 may cover thesecond encapsulation layer 852, and may be formed as a substantiallyuniform thickness along a profile of the second encapsulation layer 852.The first encapsulation layer 853 together with the first encapsulationlayer 851 and the second encapsulation layer 852 may prevent the pixelstructure form being deteriorated by the permeation of moisture, water,oxygen, etc. In addition, the first encapsulation layer 853 togetherwith the first encapsulation layer 851 and the second encapsulationlayer 852 may protect the pixel structure from external impacts. Thefirst encapsulation layer 853 may be formed using inorganic material(s).

The second encapsulation layer 854 may be formed on the firstencapsulation layer 853. The second encapsulation layer 854 may performfunctions substantially the same as or similar to those of the secondencapsulation layer 852, and the second encapsulation layer 854 mayinclude a material substantially the same as or similar to that of thesecond encapsulation layer 852. The first encapsulation layer 855 may beformed on the second encapsulation layer 854. The first encapsulationlayer 855 may perform functions substantially the same as or similar tothose of the first encapsulation layers 851 and 853, and the firstencapsulation layer 855 may include a material substantially the same asor similar to that of the first encapsulation layers 851 and 853.Accordingly, the OLED device 100 illustrated in FIG. 2 may bemanufactured.

FIG. 11 is a cross-sectional view illustrating an example of the OLEDdevice of FIG. 1, and FIG. 12 is a cross-sectional view illustratinganother example of the OLED device of FIG. 1. OLED devices illustratedin FIGS. 11 and 12 may have a configuration substantially the same as orsimilar to that of an OLED device 100 described with reference to FIG.2. Regarding FIGS. 11 and 12, detailed descriptions for elements thatare substantially the same as or similar to elements described withreference to FIG. 2 may not be repeated.

Referring to FIG. 11, an OLED device according to example embodimentsmay further include a second gate electrode 180. The second gateelectrode 180 may be interposed between the second gate insulation layer155 and the first insulating interlayer 190, and may be disposed on thesecond gate insulation layer 155 under which the first gate electrode170 is disposed. The first gate electrode 170 and the second gateelectrode 180 may serve as a capacitor. The second gate electrode 180may include one or more of a metal, a metal alloy, metal nitride,conductive metal oxide, transparent conductive material(s), etc.

Referring to FIG. 12, compared to FIG. 2, the second gate insulationlayer 155 disposed on the first gate insulation layer 150 may beomitted. In embodiments, the gate insulation layer may consistessentially of SiOx that has a refractive index in a range from 1.4 to1.5. In embodiments, the gate insulation layer may have a substantiallysingle composition of SiOx. That is, the first insulating interlayer 190may cover the first gate electrode 170 in the sub-pixel region 15, andmay be disposed on the entire first gate insulation layer 150. Forexample, the first insulating interlayer 190 may sufficiently cover thefirst gate electrode 170, and may have a substantially even surfacewithout a step around the first gate electrode 170. In an embodiment,the first insulating interlayer 190 may cover the first gate electrode170, and may be disposed as a substantially uniform thickness along aprofile of the first gate electrode 170.

FIG. 13A is a cross-sectional view illustrating an OLED device inaccordance with example embodiments, and FIG. 13B is a cross-sectionalview illustrating an OLED device in accordance with example embodiments.An OLED device 300 illustrated in FIG. 13A may have a configurationsubstantially the same as or similar to that of an OLED device 100described with reference to FIG. 2A except a second insulatinginterlayer 195. Regarding FIG. 13A, detailed descriptions for elementsthat are substantially the same as or similar to elements described withreference to FIG. 2A may not be repeated.

Referring to FIG. 13A, an OLED device 300 may include a substrate 110, abuffer layer 120, a semiconductor element 250 (e.g., a switching element250), a first gate insulation layer 150, a second gate insulation layer155, a pixel structure, a first insulating interlayer 190, a secondinsulating interlayer 195, a planarization layer 270, a pixel defininglayer 310, a thin film encapsulation layer 450, etc. Here, the substrate110 may include a polyimide layer 111 and a barrier layer 115, and thepixel structure may include a first electrode 290, a light emittinglayer 330, and a second electrode 340. In addition, the switchingelement 250 may include an active layer 130, a first gate electrode 170,a source electrode 210, and a drain electrode 230. The thin filmencapsulation layer 450 may include first encapsulation layers 451, 453,and 455 and second encapsulation layers 452 and 454.

The first insulating interlayer 190 may be disposed on the second gateinsulation layer 155. The first insulating interlayer 190 may includeorganic material(s) or inorganic material(s) that have a refractiveindex in a range from 1.7 to 1.8 (e.g., a second refractive index). Inexample embodiments, the first insulating interlayer 190 may consistessentially of SiOxNy that has a refractive index in a range from 1.7 to1.8. For example, SiOxNy may consist essentially of silicon, oxygen, andnitrogen in a weight ratio of about 3.95:1:1.7. That is, SiOxNy may beformed controlling the weight ratio such that a refractive index ofSiOxNy has a refractive index in a range from 1.7 to 1.8. In anembodiment, SiOxNy may consist essentially of silicon, oxygen, andnitrogen in a weight ratio of about 2.5:1:0.88. In embodiments, thefirst insulating interlayer 190 may have a substantially singlecomposition of SiOxNy.

In example embodiments, the second insulating interlayer 195 may beinterposed between the first insulating interlayer 190 and the sourceand drain electrodes 210 and 230, and may disposed in the sub-pixelregion 15 and the transparent region 30 on the first insulatinginterlayer 190. In addition, the second insulating interlayer 195 mayhave a refractive index in a range from 1.4 to 1.5 (e.g., a firstrefractive index).

As the second insulating interlayer 195 having the first refractiveindex that is less than the second refractive index is disposed on thefirst insulating interlayer 190 having the second refractive index, atransmittance in the transparent region 30 of the OLED device 300 may beincreased. For example, when a light is transmitted from a first layerhaving a high refractive index into a second layer having a lowrefractive index, a transmittance of a light may be increased. Inembodiments, the OLED device 300 may serve as a transparent flexibleOLED device with satisfactory transmittance.

In some example embodiments, as illustrated in FIG. 13B, the first gateinsulation layer 150 may be disposed on the active layer 130, and thesecond gate insulation layer 155 may be disposed on the first gateinsulation layer 150. In addition, the first gate electrode 170 may bedisposed on the second gate insulation layer 155. That is, the first andsecond gate insulation layer 150 and 155 may be interposed between thebuffer 120 and the gate electrode 170. In addition, the first insulatinginterlayer 190 may be disposed on the second gate insulation layer 155and the first gate electrode 170.

FIGS. 14 and 15 are graphs illustrating an average transmittance of theOLED device of FIG. 13 and an average transmittance of a comparativeexample.

Experimental Example: Evaluation on Transmittances Varying InsulationLayer Structures

A barrier layer, a buffer layer, a first gate insulation layer, a secondgate insulation layer, a first insulating interlayer, and a secondinsulating interlayer, each of which included stacked silicon oxidelayer and silicon oxynitride layer were sequentially formed on apolyimide substrate having a thickness of 10 micrometers to obtainstacked structures of Comparative Example (refer to FIG. 15).

A barrier layer having a single composition of silicon oxynitride, abuffer layer having a single composition of silicon oxide, a first gateinsulation layer having a single composition of silicon oxide, a secondgate insulation layer having a single composition of silicon oxynitride,a first insulating interlayer having a single composition of siliconoxynitride, and a second insulating interlayer having a singlecomposition of silicon oxynitride were sequentially formed on thepolyimide substrate to obtain a stacked structure of Example (refer toFIG. 14).

Specific structures of Comparative Example and Example are shown inTable 3 below. In Table 3, the silicon oxide layer, the silicon nitridelayer, and a silicon oxynitride layer are abbreviated as an oxide, anitride, and an oxynitride, respectively.

TABLE 3 Fist Gate Insulation Layer/ Second Second Gate First InsulatingInsulating Barrier Layer Buffer Layer Insulation Layer InterlayerInterlayer Comparative oxide (1,500 Å)/ nitride oxide oxide oxideExample nitride (600 Å)/ (1,000 Å)/ (750 Å)/ (3,000 Å)/ (1,000 Å) (FIG.15) oxide (1,500 Å)/ oxide nitride Nitride nitride (600 Å)/ (3,000 Å)(400 Å) (2,000 Å) oxide (1,500 Å) Example oxynitride oxide oxideoxynitride oxide (FIG. 14) (5,600 Å) (3,000 Å) (3000 Å)/ (5,000 Å)(1,000 Å) Oxynitride (400 Å)

A light was irradiated over each stacked structures of ComparativeExample and Example, and transmittances were measured. The measuredvalues are shown in Table 4 below.

TABLE 4 Comparative Example (FIG. 15) Example (FIG. 14) Average 73.25%88.2% Transmittance

As shown in Table 4, when the stacked structure having a barrier layerhaving a single composition of silicon oxynitride, a buffer layer havinga single composition of silicon oxide, a first gate insulation layerhaving a single composition of silicon oxide, a second gate insulationlayer having a single composition of silicon oxynitride, a firstinsulating interlayer having a single composition of silicon oxynitride,and a second insulating interlayer having a single composition ofsilicon oxynitride was formed, the transmittance was drasticallyincreased compared to those measured in Comparative Example, havingrepeatedly stacked different insulation layers.

FIG. 16A is a cross-sectional view illustrating an example of the OLEDdevice of FIG. 13A, and FIG. 17 is a cross-sectional view illustratinganother example of the OLED device of FIG. 13A. OLED devices illustratedin FIGS. 16A and 17 may have a configuration substantially the same asor similar to that of an OLED device 300 described with reference toFIG. 13A. Regarding FIGS. 16A and 17, detailed descriptions for elementsthat are substantially the same as or similar to elements described withreference to FIG. 13A may not be repeated.

Referring to FIGS. 16A and 17, an OLED device according to exampleembodiments may further include a second gate electrode 180. The secondgate electrode 180 may be interposed between the second gate insulationlayer 155 and the second insulating interlayer 195. For example, asillustrated in FIG. 16A, the second gate electrode 180 may be disposedon the second gate insulation layer 155 under which the first gateelectrode 170 is disposed. In some example embodiments, as illustratedin FIG. 17, the second gate electrode 180 may be disposed on the firstinsulating interlayer 190 under which the first gate electrode 170 isdisposed. The first gate electrode 170 and the second gate electrode 180may serve as a capacitor. The second gate electrode 180 may include oneor more of a metal, a metal alloy, metal nitride, conductive metaloxide, transparent conductive material(s), etc.

In some example embodiments, as illustrated in FIG. 16B, the first gateinsulation layer 150 may be disposed on the active layer 130, and thesecond gate insulation layer 155 may be disposed on the first gateinsulation layer 150. In addition, the first gate electrode 170 may bedisposed on the second gate insulation layer 155. That is, the first andsecond gate insulation layer 150 and 155 may be interposed between thebuffer 120 and the gate electrode 170. In addition, the first insulatinginterlayer 190 may be disposed on the second gate insulation layer 155and the first gate electrode 170, and the second gate electrode 180 maybe interposed between the first insulating interlayer 190 and the secondinsulating interlayer 195. That is, the second gate electrode 180 may bedisposed on the first insulating interlayer 190 under which the firstgate electrode 170 is located.

FIG. 18A is a cross-sectional view illustrating still another example ofthe OLED device of FIG. 13A. An OLED device illustrated in FIG. 18A mayhave a configuration substantially the same as or similar to that of anOLED device 300 described with reference to FIG. 13A. Regarding FIG.18A, detailed descriptions for elements that are substantially the sameas or similar to elements described with reference to FIG. 13A may notbe repeated.

Referring to FIG. 18A, an OLED device may include a substrate 110, abuffer layer 120, a semiconductor element 250 (e.g., a switching element250), a first gate insulation layer 150, a second gate insulation layer155, a pixel structure, a first insulating interlayer 190, aplanarization layer 280, a pixel defining layer 310, a thin filmencapsulation layer 450, etc. Here, the substrate 110 may include apolyimide layer 111 and a barrier layer 115, and the pixel structure mayinclude a first electrode 290, a light emitting layer 330, and a secondelectrode 340. In addition, the switching element 250 may include anactive layer 130, a first gate electrode 170, a source electrode 210,and a drain electrode 230. The thin film encapsulation layer 450 mayinclude first encapsulation layers 451, 453, and 455 and secondencapsulation layers 452 and 454.

Compared to FIG. 13A, the second insulating interlayer 195 disposed onthe first insulating interlayer 190 may be omitted.

In example embodiments, the planarization layer 280 may be disposed inthe sub-pixel region 15 and the transparent region 30 on the sourceelectrode 210, the drain electrode 230, and the first insulatinginterlayer 190. The planarization layer 280 may include organicmaterial(s) or inorganic material(s) that have a refractive index in arange from 1.4 to 1.5 (e.g., a first refractive index). Theplanarization layer 280 may have a first height H1 in the sub-pixelregion 15, and the first height H1 may extend in a third direction D3that is vertical to an upper surface of the substrate 110. Theplanarization layer 280 may have a second height H2 in the transparentregion 30, and the second height H2 extending in the third direction D3may be less than the first height H1. As the planarization layer 280having the second height H2 and the first refractive index in thetransparent region 30 is disposed, the second insulating interlayer maybe omitted. That is, the planarization layer 280 having the secondheight H2 and the first refractive index may serve as the secondinsulating interlayer 195 of FIG. 13A. Accordingly, a thickness of theOLED device may be minimized, and manufacturing cost of the OLED devicemay be minimized.

In some example embodiments, as illustrated in FIG. 18B, the first gateinsulation layer 150 may be disposed on the active layer 130, and thesecond gate insulation layer 155 may be disposed on the first gateinsulation layer 150. In addition, the first gate electrode 170 may bedisposed on the second gate insulation layer 155. That is, the first andsecond gate insulation layer 150 and 155 may be interposed between thebuffer 120 and the gate electrode 170. In addition, the first insulatinginterlayer 190 may be disposed on the second gate insulation layer 155and the first gate electrode 170.

FIG. 19A is a cross-sectional view illustrating further still anotherexample of the OLED device of FIG. 13A. An OLED device illustrated inFIG. 19A may have a configuration substantially the same as or similarto that of an OLED device 300 described with reference to FIG. 13A.Regarding FIG. 19A, detailed descriptions for elements that aresubstantially the same as or similar to elements described withreference to FIG. 13A may not be repeated.

Referring to FIG. 19A, an OLED device may include a substrate 110, abuffer layer 120, a semiconductor element 250 (e.g., a switching element250), a first gate insulation layer 150, a second gate insulation layer155, a pixel structure, a first insulating interlayer 190, aplanarization layer 270, a pixel defining layer 310, a thin filmencapsulation layer 470, etc. Here, the substrate 110 may include apolyimide layer 111 and a barrier layer 115, and the pixel structure mayinclude a first electrode 290, a light emitting layer 330, and a secondelectrode 345. In addition, the switching element 250 may include anactive layer 130, a first gate electrode 170, a source electrode 210,and a drain electrode 230. The thin film encapsulation layer 470 mayinclude first encapsulation layers 456, 458, and 460 and secondencapsulation layers 457 and 459.

Compared to FIG. 13A, the second insulating interlayer 195 disposed onthe first insulating interlayer 190 may be omitted.

In example embodiments, the second electrode 345 may be disposed on thepixel defining layer 310 and the light emitting layer 330. The secondelectrode 345 may cover the pixel defining layer 310 and the lightemitting layer 330 in the transparent region 30, and may expose thefirst insulating interlayer 190 in the transparent region 30. That is,the second electrode 345 may be disposed in the sub-pixel region 15, andmay expose the transparent region 30. The second electrode 345 mayinclude one or more of a metal, a metal alloy, metal nitride, conductivemetal oxide, transparent conductive material(s), etc.

In example embodiments, the thin film encapsulation structure 470 may bedisposed on the second electrode 345 in the sub-pixel region 15 and thefirst insulating interlayer 190 in the transparent region 30. The thinfilm encapsulation structure 470 may include at least one firstencapsulation layer and at least one second encapsulation layer. Thefirst encapsulation layers 456, 458, and 460 may include inorganicmaterial(s) that have a refractive index in a range from 1.4 to 1.5(e.g., a first refractive index). The second encapsulation layers 457and 489 may include organic material(s) that have a refractive index ina range from 1.4 to 1.5.

As the thin film encapsulation structure 470 having the first refractiveindex is disposed in the transparent region 30, the second insulatinginterlayer may be omitted. That is, the thin film encapsulationstructure 470 having the first refractive index may serve as the secondinsulating interlayer 195 of FIG. 13. Accordingly, a thickness of theOLED device may be minimized, and/or manufacturing cost of the OLEDdevice may be minimized.

In some example embodiments, as illustrated in FIG. 19B, the first gateinsulation layer 150 may be disposed on the active layer 130, and thesecond gate insulation layer 155 may be disposed on the first gateinsulation layer 150. In addition, the first gate electrode 170 may bedisposed on the second gate insulation layer 155. That is, the first andsecond gate insulation layer 150 and 155 may be interposed between thebuffer 120 and the gate electrode 170. In addition, the first insulatinginterlayer 190 may be disposed on the second gate insulation layer 155and the first gate electrode 170.

FIG. 20A is a cross-sectional view illustrating an OLED device inaccordance with example embodiments. An OLED device 500 illustrated inFIG. 20A may have a configuration substantially the same as or similarto that of an OLED device 100 described with reference to FIG. 2A excepta substrate 113 and an encapsulation substrate 400. Regarding FIG. 20A,detailed descriptions for elements that are substantially the same as orsimilar to elements described with reference to FIG. 2A may not berepeated.

Referring to FIG. 20A, an OLED device 500 may include a substrate 113, abuffer layer 120, a semiconductor element 250 (e.g., a switching element250), a first gate insulation layer 150, a second gate insulation layer155, a pixel structure, a first insulating interlayer 190, aplanarization layer 270, a pixel defining layer 310, an encapsulationsubstrate 400, etc. The pixel structure may include a first electrode290, a light emitting layer 330, and a second electrode 340, and theswitching element 250 may include an active layer 130, a first gateelectrode 170, a source electrode 210, and a drain electrode 230.

The substrate 113 may include transparent insulation material(s). Inexample embodiments, the substrate 113 may consist essentially of aglass substrate that has a refractive index in a range from 1.4 to 1.5.For example, the substrate 113 may include one or more of a quartzsubstrate, a synthetic quartz substrate, a calcium fluoride substrate, afluoride-doping quartz substrate, a soda lime substrate, a non-alkalisubstrate, etc.

The encapsulation substrate 400 may be disposed on the second electrode340. The encapsulation substrate 400 and the substrate 113 may includesubstantially the same material(s). For example, the encapsulationsubstrate 400 may include one or more of a quartz substrate, a syntheticquartz substrate, a calcium fluoride substrate, a fluoride-doping quartzsubstrate, a soda lime substrate, a non-alkali substrate, etc.

In example embodiments, each of the substrate 113, the buffer layer 120,and the first gate insulation layer 150 may have substantially the samerefractive index (value). In embodiments, as the OLED device 500 includeeach of the substrate 113, the buffer layer 120, and the first gateinsulation layer 150 that have substantially the same refractive index(value), a transmittance of the transparent region 30 may be increased.In addition, as the active layer 130 may interposed between the bufferlayer 120 and the first gate insulation layer 150 that include SiOx,interface characteristics of the active layer 130 may be improved.

In some example embodiments, as illustrated in FIG. 20B, the first gateinsulation layer 150 may be disposed on the active layer 130, and thesecond gate insulation layer 155 may be disposed on the first gateinsulation layer 150. In addition, the first gate electrode 170 may bedisposed on the second gate insulation layer 155. That is, the first andsecond gate insulation layer 150 and 155 may be interposed between thebuffer 120 and the gate electrode 170. In addition, the first insulatinginterlayer 190 may be disposed on the second gate insulation layer 155and the first gate electrode 170.

FIG. 21 is a cross-sectional view illustrating an example of the OLEDdevice of FIG. 20, and FIG. 22 is a cross-sectional view illustratinganother example of the OLED device of FIG. 21. OLED devices illustratedin FIGS. 21 and 22 may have a configuration substantially the same as orsimilar to that of an OLED device 500 described with reference to FIG.20. In FIGS. 21 and 22, detailed descriptions for elements that aresubstantially the same as or similar to elements described withreference to FIG. 20 may not be repeated.

Referring to FIG. 21, an OLED device according to example embodimentsmay further include a second gate electrode 180. The second gateelectrode 180 may be interposed between the second gate insulation layer155 and the first insulating interlayer 190, and may be disposed on thesecond gate insulation layer 155 under which the first gate electrode170 is disposed. The first gate electrode 170 and the second gateelectrode 180 may serve as a capacitor. The second gate electrode 180may include a metal, a metal alloy, metal nitride, conductive metaloxide, transparent conductive material(s), etc.

Referring to FIG. 22, compared to FIG. 20, the second gate insulationlayer 155 disposed on the first gate insulation layer 150 may beomitted. Accordingly, the gate insulation layer may consist essentiallyof (and/or may be essentially formed of) SiOx that has a refractiveindex in a range from 1.4 to 1.5. In embodiments, the gate insulationlayer may have a substantially single composition of SiOx. That is, thefirst insulating interlayer 190 may cover the first gate electrode 170in the sub-pixel region 15, and may be disposed on the entire first gateinsulation layer 150. For example, the first insulating interlayer 190may sufficiently cover the first gate electrode 170, and may have asubstantially even surface without a step around the first gateelectrode 170. In an embodiment, the first insulating interlayer 190 maycover the first gate electrode 170, and may be disposed as asubstantially uniform thickness along a profile of the first gateelectrode 170.

FIG. 23A is a cross-sectional view illustrating an OLED device inaccordance with example embodiments. An OLED device 700 illustrated inFIG. 23A may have a configuration substantially the same as or similarto that of an OLED device 500 described with reference to FIG. 20Aexcept a second insulating interlayer 195. Regarding FIG. 23A, detaileddescriptions for elements that are substantially the same as or similarto the elements described with reference to FIG. 20A may not berepeated.

Referring to FIG. 23A, an OLED device 700 may include a substrate 113, abuffer layer 120, a semiconductor element 250 (e.g., a switching element250), a first gate insulation layer 150, a second gate insulation layer155, a pixel structure, a first insulating interlayer 190, a secondinsulating interlayer 195, a planarization layer 270, a pixel defininglayer 310, an encapsulation substrate 400, etc. Here, the pixelstructure may include a first electrode 290, a light emitting layer 330,and a second electrode 340, and the switching element 250 may include anactive layer 130, a first gate electrode 170, a source electrode 210,and a drain electrode 230.

The first insulating interlayer 190 may be disposed on the second gateinsulation layer 155. The first insulating interlayer 190 may includeorganic material(s) or inorganic material(s) that have a refractiveindex in a range from 1.7 to 1.8 (e.g., a second refractive index). Inexample embodiments, the first insulating interlayer 190 may consistessentially of SiOxNy that has a refractive index in a range from 1.7 to1.8. For example, SiOxNy may consist essentially of silicon, oxygen, andnitrogen in a weight ratio of about 3.95:1:1.7. That is, SiOxNy may beformed controlling the weight ratio such that a refractive index ofSiOxNy has a refractive index in a range from 1.7 to 1.8. In anembodiment, SiOxNy may consist essentially of silicon, oxygen, andnitrogen in a weight ratio of about 2.5:1:0.88. In embodiments, thefirst insulating interlayer 190 may have a substantially singlecomposition of SiOxNy.

In example embodiments, the second insulating interlayer 195 may beinterposed between the first insulating interlayer 190 and the sourceand drain electrodes 210 and 230, and may disposed in the sub-pixelregion 15 and the transparent region 30 on the first insulatinginterlayer 190. In addition, the second insulating interlayer 195 mayhave a refractive index in a range from 1.4 to 1.5 (e.g., a firstrefractive index).

As the second insulating interlayer 195 having the first refractiveindex that is less than the second refractive index is disposed on thefirst insulating interlayer 190 having the second refractive index, atransmittance in the transparent region 30 of the OLED device 700 may beincreased. For example, when a light is transmitted from a first layerhaving a high refractive index into a second layer having a lowrefractive index, a transmittance of a light may be increased. Inembodiments, the OLED device 700 may serve as a transparent flexibleOLED device with satisfactory transmittance.

In some example embodiments, as illustrated in FIG. 33B, the first gateinsulation layer 150 may be disposed on the active layer 130, and thesecond gate insulation layer 155 may be disposed on the first gateinsulation layer 150. In addition, the first gate electrode 170 may bedisposed on the second gate insulation layer 155. That is, the first andsecond gate insulation layer 150 and 155 may be interposed between thebuffer 120 and the gate electrode 170. In addition, the first insulatinginterlayer 190 may be disposed on the second gate insulation layer 155and the first gate electrode 170.

FIG. 24A is a cross-sectional view illustrating an example of the OLEDdevice of FIG. 23A, and FIG. 25 is a cross-sectional view illustratinganother example of the OLED device of FIG. 23A. OLED devices illustratedin FIGS. 24A and 25 may have a configuration substantially the same asor similar to that of an OLED device 700 described with reference toFIG. 23A. Regarding FIGS. 24A and 25, detailed descriptions for elementsthat are substantially the same as or similar to elements described withreference to FIG. 23A may not be repeated.

Referring to FIGS. 24A and 25, an OLED device according to exampleembodiments may further include a second gate electrode 180. The secondgate electrode 180 may be interposed between the second gate insulationlayer 155 and the first insulating interlayer 190. For example, asillustrated in FIG. 24A, the second gate electrode 180 may be disposedon the second gate insulation layer 155 under which the first gateelectrode 170 is disposed. In some example embodiments, as illustratedin FIG. 25, the second gate electrode 180 may be disposed on the firstinsulating interlayer 190 under which the first gate electrode 170 isdisposed.

The first gate electrode 170 and the second gate electrode 180 may serveas a capacitor. The second gate electrode 180 may include one or more ofa metal, a metal alloy, metal nitride, conductive metal oxide,transparent conductive material(s), etc.

In some example embodiments, as illustrated in FIG. 24B, the first gateinsulation layer 150 may be disposed on the active layer 130, and thesecond gate insulation layer 155 may be disposed on the first gateinsulation layer 150. In addition, the first gate electrode 170 may bedisposed on the second gate insulation layer 155. That is, the first andsecond gate insulation layer 150 and 155 may be interposed between thebuffer 120 and the gate electrode 170. In addition, the first insulatinginterlayer 190 may be disposed on the second gate insulation layer 155and the first gate electrode 170, and the second gate electrode 180 maybe interposed between the first insulating interlayer 190 and the secondinsulating interlayer 195. That is, the second gate electrode 180 may bedisposed on the first insulating interlayer 190 under which the firstgate electrode 170 is located.

FIG. 26A is a cross-sectional view illustrating still another example ofthe OLED device of FIG. 23A. An OLED device illustrated in FIG. 26A mayhave a configuration substantially the same as or similar to that of anOLED device 700 described with reference to FIG. 23A. Regarding FIG.26A, detailed descriptions for elements that are substantially the sameas or similar to elements described with reference to FIG. 23A may notbe repeated.

Referring to FIG. 26A, an OLED device may include a substrate 113, abuffer layer 120, a semiconductor element 250 (e.g., a switching element250), a first gate insulation layer 150, a second gate insulation layer155, a pixel structure, a first insulating interlayer 190, aplanarization layer 280, a pixel defining layer 310, an encapsulationsubstrate 400, etc. Here, the pixel structure may include a firstelectrode 290, a light emitting layer 330, and a second electrode 340,and the switching element 250 may include an active layer 130, a firstgate electrode 170, a source electrode 210, and a drain electrode 230.

Compared to FIG. 23A, the second insulating interlayer 195 disposed onthe first insulating interlayer 190 may be omitted.

In example embodiments, the planarization layer 280 may be disposed inthe sub-pixel region 15 and the transparent region 30 on the sourceelectrode 210, the drain electrode 230, and the first insulatinginterlayer 190. The planarization layer 280 may include organicmaterial(s) or inorganic material(s) that have a refractive index in arange from 1.4 to 1.5 (e.g., a first refractive index). Theplanarization layer 280 may have a first height H1 in the sub-pixelregion 15, and the first height H1 may extend in a third direction D3that is vertical to an upper surface of the substrate 110. Theplanarization layer 280 may have a second height H2 in the transparentregion 30, and the second height H2 extending in the third direction D3may be less than the first height H1. As the planarization layer 280having the second height H2 and the first refractive index in thetransparent region 30 is disposed, the second insulating interlayer maybe omitted. That is, the planarization layer 280 having the secondheight H2 and the first refractive index may serve as the secondinsulating interlayer 195 of FIG. 23A. Accordingly, a thickness of theOLED device may be minimized, and/or manufacturing cost of the OLEDdevice may be minimized.

In some example embodiments, as illustrated in FIG. 13B, the first gateinsulation layer 150 may be disposed on the active layer 130, and thesecond gate insulation layer 155 may be disposed on the first gateinsulation layer 150. In addition, the first gate electrode 170 may bedisposed on the second gate insulation layer 155. That is, the first andsecond gate insulation layer 150 and 155 may be interposed between thebuffer 120 and the gate electrode 170. In addition, the first insulatinginterlayer 190 may be disposed on the second gate insulation layer 155and the first gate electrode 170.

Embodiments may be applied to various display devices, including organiclight emitting display devices. Embodiments may be applied to one ormore of in-vehicle display devices, in-ship display devices, in-aircraftdisplay devices, portable communication devices, display devices forinformation transfer, medical display devices, etc.

The foregoing is illustrative of example embodiments and is not to beconstrued as limiting. Although example embodiments have been described,those skilled in the art will readily appreciate that many modificationsare possible in the example embodiments. All such modifications areintended to be included within the scope defined in the claims.

What is claimed is:
 1. An organic light emitting display (OLED) device, comprising: a substrate including a sub-pixel region and a transparent region; a buffer layer in the sub-pixel region and the transparent region on the substrate, the buffer layer having a first refractive index; a first gate insulation layer in the sub-pixel region and the transparent region on the buffer layer, the first gate insulation layer including the same material with the buffer layer; an active layer between the buffer layer and the first gate insulation layer; a first gate electrode on the first gate insulation layer under which the active layer is disposed; a first insulating interlayer covering the gate electrode on the first gate insulation layer, the first insulating interlayer being in the sub-pixel region and the transparent region, the first insulating interlayer having a second refractive index that is greater than the first refractive index; source and drain electrodes on the first insulating interlayer, the source and drain electrodes defining a semiconductor element together with the active layer and the first gate electrode; and a pixel structure on the semiconductor element, the pixel structure being electrically connected to the semiconductor element.
 2. The OLED device of claim 1, wherein the first refractive index is in a range between about 1.4 and about 1.5, and the second refractive index is in a range between about 1.7 and about 1.8, and wherein an upper surface of the active layer is in contact with the first gate insulation layer, and a lower surface of the active layer is in contact with the buffer layer.
 3. The OLED device of claim 1, wherein the substrate includes transparent insulation materials.
 4. The OLED device of claim 3, wherein the substrate consists essentially of a transparent polyimide substrate that has a refractive index in a range between about 1.7 and about 1.8.
 5. The OLED device of claim 4, wherein the substrate includes a transparent polyimide layer and a barrier layer, and the barrier layer is interposed between the transparent polyimide layer and the buffer layer, and wherein the barrier layer and the first insulating interlayer include the same material.
 6. The OLED device of claim 5, wherein the barrier layer consists essentially of silicon oxynitride that has a refractive index in a range between about 1.7 and about 1.8, and wherein the silicon oxynitride consists essentially of silicon, oxygen, and nitrogen in a respective weight ratio of about 3.95:1:1.7.
 7. The OLED device of claim 4, wherein each of the buffer layer and the first gate insulation layer consists essentially of silicon oxide that has a refractive index in a range between about 1.4 and about 1.5.
 8. The OLED device of claim 4, wherein the active layer consists essentially of amorphous silicon or polysilicon.
 9. The OLED device of claim 4, wherein the first insulating interlayer consists essentially of silicon oxynitride that has a refractive index in a range between about 1.7 and about 1.8, and. wherein the silicon oxynitride consists essentially of silicon, oxygen, and nitrogen in a respective weight ratio of about 3.95:1:1.7.
 10. The OLED device of claim 4, further comprising: a second gate insulation layer interposed between the first gate insulation layer and the first insulating interlayer, the second gate insulation layer being in the sub-pixel region and the transparent region, wherein the second gate insulation layer and the first insulating interlayer include the same material.
 11. The OLED device of claim 10, wherein the second gate insulation layer consists essentially of silicon oxynitride that has a refractive index in a range between about 1.7 and about 1.8, and wherein the silicon oxynitride consists essentially of silicon, oxygen, and nitrogen in a respective weight ratio of about 3.95:1:1.7.
 12. The OLED device of claim 10, further comprising: a second gate electrode interposed between the second gate insulation layer and the first insulating interlayer, the second gate electrode being on the second gate insulation layer under which the first gate electrode.
 13. The OLED device of claim 4, further comprising: a second gate insulation layer interposed between the first gate insulation layer and the first insulating interlayer, the second gate insulation layer being in the sub-pixel region and the transparent region, wherein the first and second gate insulation layers are interposed between the buffer layer and the first gate electrode, and wherein the second gate insulation interlayer consists essentially of silicon oxynitride that has a refractive index in a range between about 1.7 and about 1.8, and the silicon oxynitride consists essentially of silicon, oxygen, and nitrogen in a respective weight ratio of about 3.95:1:1.7.
 14. The OLED device of claim 13, further comprising: a second insulating interlayer interposed between the first insulating interlayer and the source and drain electrodes, the second insulating interlayer being in the sub-pixel region and the transparent region, the second insulating interlayer having the first refractive index, wherein the second insulating interlayer consists essentially of silicon oxide that has a refractive index in a range between about 1.4 and about 1.5.
 15. The OLED device of claim 14, further comprising: a second gate electrode interposed between the first insulating interlayer and the second insulating interlayer, the second gate electrode being on the first insulating interlayer under which the first gate electrode is disposed.
 16. The OLED device of claim 4, further comprising: a second insulating interlayer interposed between the first insulating interlayer and the source and drain electrodes, the second insulating interlayer being in the sub-pixel region and the transparent region, the second insulating interlayer having the first refractive index, wherein the second insulating interlayer consists essentially of silicon oxide that has a refractive index in a range between about 1.4 and about 1.5.
 17. The OLED device of claim 16, further comprising: a second gate electrode interposed between the first insulating interlayer and the second insulating interlayer, the second gate electrode being on the first insulating interlayer under which the first gate electrode is disposed.
 18. The OLED device of claim 4, further comprising: a planarization layer covering the source and drain electrodes on the first insulating interlayer.
 19. The OLED device of claim 18, wherein the planarization layer is disposed in the sub-pixel region on the first insulating interlayer, and exposes the transparent region.
 20. The OLED device of claim 18, wherein the planarization layer is disposed in the sub-pixel region and the transparent region on the first insulating interlayer, and has the first refractive index, wherein the planarization layer has a first height in the sub-pixel region, and the first height extends in a direction that is vertical to an upper surface of the substrate, and wherein the planarization layer has a second height in the transparent region, and the second height extending in the direction is less than the first height.
 21. The OLED device of claim 4, wherein the pixel structure includes: a first electrode on the first insulating interlayer; a light emitting layer on the first electrode; and a second electrode on the light emitting layer.
 22. The OLED device of claim 21, wherein the second electrode is disposed in the sub-pixel region and the transparent region.
 23. The OLED device of claim 21, further comprising: a thin film encapsulation structure on the pixel structure, the thin film encapsulation structure including at least one a first encapsulation layer and at least one a second encapsulation layer, wherein the first and second encapsulation layers are alternately arranged, wherein the first encapsulation layer includes inorganic materials that have a refractive index in a range between about 1.4 and about 1.6, and wherein the second encapsulation layer includes organic materials that have a refractive index in a range between about 1.4 and about 1.6.
 24. The OLED device of claim 23, wherein the first encapsulation layer includes silicon oxynitride.
 25. The OLED device of claim 23, wherein the second electrode is disposed in the sub-pixel region, and exposes the transparent region, and wherein the thin film encapsulation structure is in contact with the first insulating interlayer in the transparent region.
 26. The OLED device of claim 3, wherein the substrate consists essentially of a glass substrate that has a refractive index in a range between about 1.4 and about 1.5.
 27. The OLED device of claim 26, wherein the buffer layer and the first gate insulation layer consist essentially of silicon oxide that has a refractive index in a range between about 1.4 and about 1.5, wherein the active layer consists essentially of amorphous silicon or poly silicon, wherein the first insulating interlayer consists essentially of silicon oxynitride that has a refractive index in a range between about 1.7 and about 1.8, and wherein the silicon oxynitride consists essentially of silicon, oxygen, and nitrogen in a respective weight ratio of about 3.95:1:1.7.
 28. The OLED device of claim 26, further comprising: a second gate insulation layer interposed between the first gate insulation layer and the first insulating interlayer, the second gate insulation layer being in the sub-pixel region and the transparent region, wherein the second gate insulation layer consists essentially of silicon oxynitride that has a refractive index in a range between about 1.7 and about 1.8, and wherein silicon oxynitride consists essentially of silicon, oxygen, and nitrogen in a respective weight ratio of about 3.95:1:1.7.
 29. The OLED device of claim 27, further comprising: a second electrode interposed between the second gate insulation layer and the first insulating interlayer, the second electrode being on the second gate insulation layer under which the first gate electrode is disposed.
 30. The OLED device of claim 26, further comprising: a second gate insulation layer interposed between the first gate insulation layer and the first insulating interlayer, the second gate insulation layer being in the sub-pixel region and the transparent region, wherein the first and second gate insulation layers are interposed between the buffer layer and the first gate electrode, and wherein the second gate insulation interlayer consists essentially of silicon oxynitride that has a refractive index in a range between about 1.7 and about 1.8, and the silicon oxynitride consists essentially of silicon, oxygen, and nitrogen in a respective weight ratio of about 3.95:1:1.7.
 31. The OLED device of claim 30, further comprising: a second insulating interlayer interposed between the first insulating interlayer and the source and drain electrodes, the second insulating interlayer being in the sub-pixel region and the transparent region, the second insulating interlayer having the first refractive index, wherein the second insulating interlayer consists essentially of silicon oxide that has a refractive index in a range between about 1.4 and about 1.5.
 32. The OLED device of claim 31, further comprising: a second gate electrode interposed between the first insulating interlayer and the second insulating interlayer, the second gate electrode being on the first insulating interlayer under which the first gate electrode is disposed.
 33. The OLED device of claim 26, further comprising: a second insulating interlayer interposed between the first insulating interlayer and the source and drain electrodes, the second insulating interlayer being in the sub-pixel region and the transparent region, the second insulating interlayer having the first refractive index, wherein the second insulating interlayer consists essentially of silicon oxide that has a refractive index in a range between about 1.4 and about 1.5.
 34. The OLED device of claim 33, further comprising: a second gate electrode interposed between the first insulating interlayer and the second insulating interlayer, the second gate electrode being on the first insulating interlayer under which the first gate electrode is disposed.
 35. The OLED device of claim 26, further comprising: a planarization layer covering the source and drain electrodes on the first insulating interlayer.
 36. The OLED device of claim 35, wherein the planarization layer is disposed in the sub-pixel region on the first insulating interlayer, and exposes the transparent region.
 37. The OLED device of claim 35, wherein the planarization layer is disposed in the sub-pixel region and the transparent region on the first insulating interlayer, and has the first refractive index, and wherein the planarization layer has a first height in the sub-pixel region, and the first height extends in a direction that is vertical to an upper surface of the substrate, and wherein the planarization layer has a second height in the transparent region, and the second height extending in the direction is less than the first height.
 38. The OLED device of claim 26, wherein the pixel structure includes: a first electrode on the first insulating interlayer; a light emitting layer on the first electrode; and a second electrode on the light emitting layer, and wherein the second electrode is disposed in the sub-pixel region and the transparent region.
 39. A display device comprising: a light emitting element; a buffer layer; a first gate insulation layer, wherein a refractive index of the first gate insulation layer is equal to a refractive index of the buffer layer; and a switching element, which is electrically connected to the light emitting element, comprises an active layer, and comprises a first gate electrode, wherein the active layer is positioned between the buffer layer and the first gate insulation layer and directly contacts at least one of the buffer layer and the first gate insulation layer, wherein the first gate insulation layer is positioned between the active layer and the first gate electrode and directly contacts at least one of the active layer and the first gate electrode.
 40. The display device of claim 39 comprising: a pixel defining layer, which has a first opening, wherein the active layer is positioned between a first portion of the buffer layer and a first portion of the first gate insulation layer in a direction perpendicular to a side of the buffer layer, and wherein a second portion of the first gate insulation layer is positioned between a second portion of the buffer layer and the first opening in the direction perpendicular to a side of the buffer layer.
 41. The display device of claim 39, wherein the buffer layer directly contacts the first gate insulation layer and includes no nitride, and wherein a material of the buffer layer is identical to a material of the first gate insulation layer.
 42. The display device of claim 39, wherein the refractive index of the buffer layer is greater than or equal to 1.4 and is less than or equal to 1.5.
 43. The display device of claim 39 comprising: a first insulating interlayer, wherein the first gate electrode is positioned between the first gate insulation layer and the first insulating interlayer, and wherein a refractive index of the first insulating interlayer is greater than the refractive index of the first gate insulation layer.
 44. The display device of claim 43, wherein a difference between the refractive index of the first insulating interlayer and the refractive index of the first gate insulation layer is greater than or equal to 0.2 and is less than or equal to 0.4.
 45. The display device of claim 44, wherein the refractive index of the first insulating interlayer is greater than or equal to 1.7 and is less than or equal to 1.8.
 46. The display device of claim 44, wherein the first insulating interlayer directly contacts each of the first gate electrode and the first gate insulation layer.
 47. The display device of claim 43 comprising: a second gate insulation layer, which directly contacts the first insulating interlayer and is positioned between the first gate electrode and the first insulating interlayer, wherein a refractive index of the second gate insulation layer is equal to the refractive index of the first insulating interlayer.
 48. The display device of claim 47 comprising: a pixel defining layer, which has a first opening, wherein a first portion of the second gate insulation layer is positioned between the first gate electrode and a first portion of the first insulating interlayer in a direction perpendicular to a side of the buffer layer and directly contacts the first portion of the first insulating interlayer, and wherein a second portion of the first insulating interlayer is positioned between a second portion of the second gate insulation layer and the first opening in the direction perpendicular to the side of the buffer layer.
 49. The display device of claim 47 comprising: a second gate electrode, which is positioned between the second gate insulation layer and the first insulating interlayer and directly contacts at least one of the second gate insulation layer and the first insulating interlayer.
 50. The display device of claim 43 comprising: a second insulating interlayer, wherein the first insulating interlayer is positioned between the first gate electrode and the second insulating interlayer and directly contacts the second insulating interlayer, and wherein a refractive index of the second insulating interlayer is less than the refractive index of the first insulating interlayer.
 51. The display device of claim 50, wherein a difference between the refractive index of the first insulating interlayer and the refractive index of the second insulating interlayer is greater than or equal to 0.2 and is less than or equal to 0.4.
 52. The display device of claim 50, wherein the refractive index of the second insulating interlayer is equal to the refractive index of the buffer layer.
 53. The display device of claim 50 comprising: a second gate electrode, which is positioned between the first insulating interlayer and the second insulating interlayer and directly contacts at least one of the first insulating interlayer and the second insulating interlayer.
 54. The display device of claim 43 comprising: a transparent substrate, wherein a refractive index of the transparent substrate is equal to the refractive index of the first insulating interlayer or the refractive index of the buffer layer.
 55. The display device of claim 43 comprising: a transparent polyimide layer; and a barrier layer, which is positioned between the transparent polyimide layer and the buffer layer, wherein the buffer layer is positioned between the barrier layer and the active layer, and wherein a refractive index of the barrier layer is equal to the refractive index of the first insulating interlayer.
 56. The display device of claim 55, wherein a material of the barrier layer is identical to a material of the first insulating interlayer, and wherein a weight proportion of silicon, oxygen, and nitrogen of the material of the barrier layer is 3.95:1:1.7.
 57. The display device of claim 43 comprising: an encapsulation layer, wherein a refractive index of the encapsulation layer is equal to the refractive index of the first insulating interlayer or the refractive index of the buffer layer, and wherein the light emitting element is positioned between the first insulating interlayer and the encapsulation layer.
 58. The display device of claim 43 comprising: an inorganic material layer, wherein a refractive index of the inorganic material layer is equal to the refractive index of the first insulating interlayer or the refractive index of the buffer layer; and an organic material layer, which directly contacts the inorganic layer, wherein one of the inorganic material layer and the organic material layer directly contacts the first insulating interlayer and is positioned between the light emitting element and another of the inorganic material layer and the organic material layer. 